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)V 


PHYSICAL  CHEMISTRY 


SERVICE   OF    MEDICINE 


SEVEN  ADDRESSES 

BY 

Dr.    WOLFGANG    PAULI 

Privatdocent  in  Internal  Medicine  at  the  University  of  Vienna 
AUTHORIZED    TRANSLATION     BY 

Dr.   MARTIN    H.   FISCHER 

Professor  of  Pathology  at  lite  Oakland  College  of  Medicine 


FIKST    EDITION 
FIRST    THOUSAND 


NEW   YORK 
JOHN    WILEY    &    SONS 

London:    CHAPMAN   &    HALL,    Limited 
1907 


Copyright,  1906 


MARTIN   H.   FISCHER 


T1\ 


ROBERT   DRUMMOND,    PRINTER,   NEW   YORK 


AUTHOR'S    PREFACE. 


The  addresses  which  have  been  collected  for  the 
first  time  in  this  volume  and  which  were  delivered  in 
the  main  as  summaries  of  my  own  special  investigations 
concern  themselves  with  the  application  of  physical 
chemistry  to  different  fields  in  medicine  as  rendered 
possible  more  particularly  through  advances  in  the 
physics  and  chemistry  of  organic  colloids.  In  that 
questions  in  physiology  as  well  as  pathology  and 
pharmacology  are  touched  upon,  it  may  perhaps  be 
hoped  that  different  circles  of  medical  men  may  be 
interested  in  the  problems  discussed  in  this  volume. 
The  translated  addresses  differ  in  only  a  few  unimpor- 
tant abbreviations  from  the  original.  The  development 
of  the  guiding  thought  common  to  all  of  them  stands 
out  quite  clearly.  Its  foundation  is  the  extensive 
parallelism  between  the  laws  which  govern  changes  in 
the  colloidal  state  in  vitro  and  in  the  living  orga)i ism. 
~  Even  though  the  future  may  become  acquainted  with 
many  a  new  fact  through  which  the  questions  discussed 

J7  in  this  volume  mav  be  made  to  appear  in  a  different 
light,  it  will  scarcely  be  possible  to  belittle  the  fruit  ful- 
ness of  the  methods  described  and  the  stimulating  effect 

i-  ili 


iv  AUTHOR'S  PREFACE. 

of  the  results  obtained  through  them.  Since  all  the 
results  that  these  methods  can  yield  are  as  yet  by  no 
means  attained  it  is  hoped  that  the  volume  may  be 
looked  upon  as  a  modest  attempt  to  win  friends  capa- 
ble of  work  in  this  still  young  field  of  labor. 

Wolfgang  Pauli. 

Vienna,  May  i,  1906. 


TRANSLATOR'S   PREFACE. 


It  is  hoped  that  the  following  translation  of  a  few 
of  Dr.  Pauli's  papers  may  render  some  of  the  work  of 
this  modest  Viennese  investigator  already  familiar  to 
a  large  circle  of  American  and  English  workers  accessi- 
ble to  yet  others.  The  fundamental  character  of  the 
subjects  touched  upon  by  the  author  needs  no  com- 
ment. It  is  only  hoped  that  the  translation  may  not 
have  lost  too  much  of  the  spirit  and  the  letter  of  the 
original  German.  The  volume  as  a  whole  represents 
another  stone  in  the  structure  of  physical  chemistrv 
in  the  biological  sciences;  and  while  it  is  not  the 
tendency  of  modern  times  to  divide  existing  sciences 
or  to  create  new  ones,  specialism  is  followed  as  a 
matter  of  necessity,  so  that  it  will  not  seem  strange  if 
in  the  near  future  we  shall  come  to  recognize  as  branches 
developing  separately  from  the  trunk  which  all  these 
sciences  have  in  common,  a  physico-chemical  physiology 
and  a  physico-chemical  pathology. 

Martin  H.  Fischer. 

Oakland,  California. 

v 


PREFATORY  NOTE  TO   AMERICAN 
EDITION. 


The  advance  of  medicine  is  so  dependent  upon 
progress  in  the  fundamental  sciences  of  physics,  chem- 
istry, and  biology  that  he  who  will  keep  abreast  of 
modern  conceptions  in  physiology  and  pathology  is 
compelled  to  be  more  or  less  conversant  with  theory 
and  practice  in  the  basal  subjects.  When  one  con- 
siders  the  phenomenal  development  in  recent  years, 
through  the  work  especially  of  Willard  Gibbs,  van't  Hoff, 
and  Arrhenius,  in  the  domain  of  what  is  designated 
physical  chemistry,  it  is  not  surprising  that  attempts 
should  have  been  made  to  apply  the  new  knowledge 
gained  to  the  clearing  up  of  some  of  the  problems 
which  confront  the  physician.  While  the  application 
of  stoichiometrical  methods  in  medicine  and  biology 
has  led  and  is  leading  to  fruitful  results,  it  is  from 
the  utilization  of  the  principles  of  the  other  great  branch 
of  physical  chemistry,  that  which  deals  with  energy- 
relations  in  chemical  processes,  that  most  is  to  be 
hoped;  that  many  of  the  medical  conceptions  of  the 
future  are  to  be  colored  by  the  ideas  of  thermochem- 
istry, electrochemistry,  chemical  kinetics,  and  chemical 
dynamics  even  those  of  us  who  are  entirely  untrained 
in  these  sciences  are  compelled  to  admit.  The  work 
already  done  on  reaction-velocity,  catalysis,  equilibrium, 
viscosity,   osmotic  pressure,  and  electrolytic  dissocia- 


Vlll        PREFATORY  NOTE   TO  AMERICAN  EDITION. 

tion  in  the  human  and  animal  body  may  be  regarded 
as  an  earnest-penny  of  greater  good  hereafter. 

The  new  medicine  will  require  a  new  preliminary 
training  of  its  workers.  A  few  investigators  in  biology 
and  medicine  have  been  wise  enough  to  foresee  the 
path  which  future  inquiries  must  follow;  we  should 
be  thankful  that  they  have  prepared  themselves  for 
the  pioneer  work  of  blazing  the  trail.  Notable 
among  these  hardy  explorers  are  some  of  our  fore- 
most American  workers  in  physiology.  Among  Euro- 
pean scientists,  Dr.  W.  Pauli  of  Vienna  stands  out 
prominently  as  a  representative  of  the  forward  move- 
ment. His  researches  in  physiology  and  pharmacology 
have  dealt  almost  entirely  with  problems  in  the  solu- 
tion of  which  the  methods  of  physical  chemistry  have 
been  applied.  In  his  recent  studies  in  colloidal  chem- 
istry he  has  been  prying  into  and  attempting  to  illu- 
minate some  of  the  darkest  of  the  regions  in  which 
physiological  chemists  grope. 

The  American  publishers  of  Dr.  Pauli's  papers  have 
been  fortunate  in  securing  the  services  of  Dr.  Martin 
Fischer  as  translator.  The  experience  he  has  gained 
by  his  personal  researches  in  similar  fields,  and  his 
familiarity  with  the  bibliography  of  the  whole  sub- 
ject, especially  fit  him  for  the  task. 

May  Dr.  Pauli's  papers  stimulate  American  stu- 
dents to  further  investigations  where  they  are  so  much 
needed,  and  may  he  and  they  collect  speedily  for  us 
a  body  of  facts  which  we,  as  medical  men,  may  utilize 
in  the  diagnosis  of  disease  and  the  cure  of  human  ills! 

Lewellys  F.  Barker. 

Baltimore,  Oct.  23,  1906, 


CONTENTS. 


PAGE 

i.     On  Physico-chemical  Methods  and  Problems  in  Medi- 

I   !  \  I I 

2.  The   General   Physical   Chemistry  of  the  Cells   and 

Tissues 23 

3.  The  Colloidal  State  and  the  Reactions  that  Go  on 

in  Living   Matter 44 

4.  Therapeutic   Studies   on   Ions 71 

5.  On  the  Relation  between  Physico-chemical  Properties 

and  Medicinal  Effects 90 

6.  Changes    Wrought    in    Pathology    through    Advances 

in   Physical   Chemistry 101 

7.  On  the  Electrical  Charge  of  Protein  and  its  Signifi- 

cance     137 

ix 


PHYSICAL    CHEMISTRY    IN    THE 
SERVICE   OF   MEDICINE. 


I.  On  Physico-chemical  Methods  and  Problems  in 
Medicine.* 

The  last  decades  have  brought  with  them  an  amal- 
gamation of  two  sciences, — physics  and  chemistry, — 
which  have  no  doubt  always  had  mutual  relations, 
although  formerly  these  were  not  so  intimate  or  extensive 
as  they  are  now. 

This  amalgamation  was  undoubtedly  inaugurated 
through  physics,  and  must  be  attributed  primarily  to 
the  stimulus  which  brought  with  it  the  establishment  of 
the  laws  of  thermodynamics. 

I  cannot  here  sketch  even  briefly  the  development  of 
thermodynamics.  As  is  well  known,  the  law  of  the 
conservation  of  energy  as  most  clearly  enunciated  by 
M  \vi  r  forms  its  foundation.  The  remarkable  experi- 
ments  of  Joule    next    led    to    an    exact   determination 

*  t'ber  physikalisch-chcmischo  Methoden  un<]  Probleme  in  der 
Medicin,  Wicn,  iqoo,  M.  Perles.  Address  delivered  to  the  A',  k. 
Gcsrllschaft  der  Aerzic,  Vienna,  November  10,  1899. 


2  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

of  the  mechanical  equivalent  of  heat,  while  through 
Helmholtz  was  developed  and  executed  the  most 
extensive  programme  for  the  application  of  the  law  of 
energy  to  all  subjects. 

The  penetrative  analysis  of  thermodynamical  phenom- 
ena by  Clausius  and  Thomson  completed  the  subject 
with  the  establishment  of  the  so-called  chief  laws  of 
thermodynamics. 

The  transformations  in  energy  in  chemical  reactions 
have  in  general  two  sources.  As  is  well  known  every 
change  in  the  state  of  aggregation  is  accompanied  by 
either  an  absorption  or  an  evolution  of  heat.  Since 
changes  in  physical  state  often  accompany  a  chemical 
reaction,  these  constitute  therefore  one  of  the  sources 
of  the  transformations  in  energy  accompanying  this 
reaction. 

A  second  is  found  in  the  chemical  reaction  itself. 
The  synthesis  or  analysis  of  a  substance  is  accompanied 
by  a  thermal  change  which  may  have  either  a  positive 
or  a  negative  value.  To  illustrate  this  we  may  cite  the 
formation  of  a  salt  from  an  acid  and  a  base  with  the 
development  of  the  so-called  heat  of  neutralization;  or 
the  decomposition  of  a  salt  into  its  components  with  a 
using  up  of  electrical  energy. 

All  these  metamorphoses  in  energy  constituted  from 
the  first  a  fruitful  field  for  work,  in  which  medicine 
also  soon  took  part.  While,  however,  the  decrease 
in  the  potential  energy  of  the  foodstuffs  in  the  metabolism 
of  men  and  the  higher  animals  constitutes  one  of  the 
best  developed  chapters  of  medicine,  calorimetric  in- 
vestigations of  the  culture  media  of  bacteria  are  still 
lacking,  and  this  in  spite  of  the  fact  that  this  subject 


ON  PHYSICO-CHEMICAL   METHODS   AND    PROBLEMS.        3 

promises  the  solution  of  an  Important  problem,  namely, 
the  energy  of  growth. 

Further  relations  between  chemical  constitution  and 
physical  properties  were  discovered  by  the  new  science, 
physical  or  theoretical  chemistry. 

Under  this  heading  must  be  mentioned  first  of  all 
the  connection  discovered  between  optical  asymmetry 
(rotation  of  the  plane  of  polarized  light)  and  asymmetry 
in  chemical  composition.  At  almost  the  same  time 
Le  Bel  and  van't  Hoff  discovered  that  all  optically 
active  substances  which  in  the  non-crystalline  state 
rotate  the  plane  of  polarized  light  contain  an  asymmetric 
carbon  atom,  the  four  valencies  of  which  are  connected 
with  four  different  radicles.  If  we  imagine  these  four 
valencies  connected  with  the  corners  of  a  tetrahedron, 
the  four  radicles  may  be  grouped  in  two  different  ways 
and  be  symmetrical.  The  development  of  this  idea, 
which  constitutes  the  foundation  of  stereochemistry,  has 
been  very  fruitful. 

The  doctrine  of  the  asymmetrical  carbon  atom  is 
destined  to  play  an  important  role  in  biological  problems 
also,  for  such  essential  constituents  of  protoplasm  as  the 
proteins  and  many  carbohydrates  must,  to  correspond 
with  their  optical  activity,  contain  such  an  asymmetrical 
carbon  atom. 

The  connection  between  physical  changes  in  state  and 
chemical  constitution  was  early  indicated  by  the  regu- 
larity with  which  bodies  of  the  aliphatic  series  affect 
the  boiling-point.  More  recently  a  connection  between 
color  and  the  position  of  certain  groups  in  the  molecule 
known  as  chromophores  has  been  discovered.  Similar 
conditions  exist   in   the   case  of  fluorescence   which    is 


4  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

connected  with  the  existence  of  fluorophore  radicles, 
and  in  the  case  of  antipyretics  the  effect  of  which  is 
intimately  associated  with  their  chemical  constitution. 

The  modern  theory  of  solution  as  harmoniously 
enlarged  through  van't  Hoff's  conception  of  the  gas- 
like condition  of  the  dissolved  particles,  and  Arrhenius's 
teaching  that  electrolytes — salts,  acids,  and  bases — dis- 
sociate upon  solution  into  their  constituent  ions,  has 
also  found  extensive  scientific  application  to  many 
subjects  including  medicine. 

Following  the  establishment  of  these  fundamental 
facts  physical  chemistry  has  developed  as  an  independent 
science  with  numerous  methods  of  experiment  peculiar 
to  itself  and  adapted  to  its  own  special  purposes. 

Medicine  has  at  no  time  denied  its  dependence  upon 
advances  in  the  exact  sciences,  and  so  it  is  not  strange 
to  find  that  with  new  ideas  in  physics  there  have  come 
corresponding  periods  of  discovery  in  medicine.  But 
the  application  of  newly  discovered  facts  in  physics 
to  medical  problems  for  the  solution  of  which  they  were 
never  intended  has  as  a  rule  brought  it  to  pass  that  every 
era  of  progress  has  been  followed  by  one  of  disappoint- 
ment, a  period  characterized  by  an  overgrowth  of  specu- 
lation and  hypothesis. 

The  great  development  of  mechanics  in  the  seventeenth 
century  associated  with  the  names  of  Stevin,  Galilei, 
Kepler,  Descartes,  Huyghens,  and  many  others  fruc- 
tified the  epoch  of  the  iatro-physicists  whose  accomplish- 
ments as  evidenced  by  their  work  on  the  mechanics  of 
joints  and  the  development  of  Harvey's  teaching  of  the 
circulation  have  lasted  into   modern  times.     But   even 


ON  PHYSICO  CHEMICAL   MB 7 HODS   AND  PROBLEMS.        5 

as  late  as  the  eighteenth  century  greal  physicists  such  as 
Johannes  Bernoulli  attempted  the  solution  of  such 
subjects  as   Dissertationes   physico  mechanicae  <lc   motu 

musculorum  et  dc  cfjcrvcscaUia  el  jcnucntiilionc. 

In  the  first  half  of  the  nineteenth  century  the  great 
development  of  physics,  more  especially  electricity, 
favored  the  wonderful  development  of  physical  physi- 
ology which  began  its  career  in  Germany. 

But  both  these  times  physics  were  insufficient  to  exhaust 
the  problem  of  life,  and  the  fully  developed  reaction  to  the 
iatro-mechanical  school  finds  counterpart  in  the  reaction 
of  modern  times,  the  participants  of  which  are  divided 
between  two  camps.  The  belief  of  one  of  these,  the 
neovitalists,  can  be  traced  back  to  the  "anima"  of 
Georg  Ernst  Statil.  In  this  teaching  vital  force 
which  has  been  so  often  pronounced  dead  is  born  again. 
The  second  group,  not  less  dangerous  than  the  first, 
employs  an  atomic  mechanics  for  the  explanation  of  life 
phenomena,  and  mistakes  the  death-dance  of  the  mole- 
cules for  living  reality. 

In  this  time  of  threatening  retrogression  the  seeds  of 
modern  physical  chemistry  fall  upon  that  narrow  field 
of  endeavor  which  we  call  our  own.  But  if  this  new 
and  flourishing  science  is  not  also  to  prove  a  hindrance 
to  investigation  by  exceeding  its  natural  limits,  it  is  well 
that  we  define  first  of  all  the  boundaries  within  which  its 
laws  hold  in  biological  questions. 

Let  us  attempt  first  of  all  to  get  a  conception  of  the 
significance  of  the  law  of  the  conservation  of  energy  as  a 
means  of  biological  research.  This  attempt  seems  all 
the  more  justified  since  OsTWALD,  whose  great  services 
in   the  development  of   physical  chemistry  demand   the 


6  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

widest  recognition,  has  already  proclaimed  the  complete 
triumph  of  the  energetische  Weltanschauung  (energetic 
conception  of  natural  phenomena). 

According  to  this  conception  transformations  in  energy 
constitute  the  kernel  of  all  phenomena  in  nature,  and 
their  quantitative  determination  furnishes  at  the  same 
time  a  complete  insight  into  the  course  of  things. 

If  this  is  true,  then  the  reaction  of  the  sensory  nerves 
is  also  always  a  consequence  of  changes  in  energy  and 
these  become  therefore  the  means  by  which  sensory 
experience  is  obtained. 

An  attempt  will  be  made  in  the  following  paragraphs 
to  show  that  a  purely  energetic  conception  of  natural 
phenomena  conceals  all  the  dangers  of  a  too  extensive 
generalization,  as  it  leads  to  a  one-sided  development 
of  our  point  of  view  with  all  its  threatening  consequences. 

Do  transformations  in  energy  really  constitute  the  whole 
or  even  the  nucleus  of  the  changes  that  go  on,  in  and 
about  us?  Do  we  really  react  only  in  proportion  to  the 
amount  of  difference  in  energy  ? 

Transformations  in  energy  are  in  fact  constant  accom- 
paniments of  all  changes  in  nature,  and  we  could  scarcely 
possess  a  simpler  picture  of  nature  than  one  in  which  all 
differences  represent  only  differences  in  the  amount  of 
of  energy.  In  reality,  however,  it  is  only  one  side  of  all 
natural  phenomena  that  we  are  able  to  include  in  the 
energetic  principle,  for  only  for  the  value  of  the  mechanical 
work  performed  in  all  changes  does  the  law  of  its  inde- 
structibility hold.  The  energetic  analysis  of  a  phe- 
nomenon is,  however,  so  little'  exhaustive  that  in  physical 
realms,  such  as  that  of  electricity  for  example,  we  are 
unable  to  answer  the  question  of  the  nature  of  electrical 


ON  PHYSICO-CHEMICAL   METHODS  AND  PROBLEMS.       7 

phenomena  in  spite  of  most  extensive  utilization  of  the 
M  w  ik  Jm  i  i  law. 

The  energetic  principle  suffices  equally  little  in  bio- 
logical questions,  and  we  must  regard  the  attempt  of  an 
excellent  investigator  to  define  general  physiology  as 
the  energetics  of  life  phenomena  as  not  sufficiently 
comprehensive.  Our  law  determines  only  the  energy  value 
corresponding  with  the  changes  that  take  place  in  living 
matter;  the  fundamental  question  of  their  nature  remains 
entirely  unanswered. 

A  picture  of  natural  phenomena  which  shows  only 
differences  in  energy  is  as  incomplete  as  a  photograph 
which  shows  only  differences  in  light  and  shade. 

Upon  the  second  assertion  of  Ostwald  that  we  react 
only  in  proportion  to  differences  in  energy  we  must  also 
place  certain  limitations. 

What  we  designate  as  external  stimuli  are  changes 
which  also  are  connected  with  variations  in  energy.  The 
important  point  in  our  question  is  whether  differences 
in  energy  determine  quantitatively  the  excitation  value 
of  a  stimulus.  If  this  is  true,  then  electrical,  thermal,  or 
mechanical  stimuli  having  the  same  energy  value  ought 
to  possess  the  same  excitation  value.  Things  are  by 
no  means  as  simple  as  this,  however.  We  do  not  per- 
ceive the  energy  communicated  to  our  sense-organs 
directly.  What  we  perceive  are  only  changes  in  the 
state  of  our  sensory  nerves,  a  fact  recognized  by  Descartes 
in  his  day  and,  as  pointed  out  by  Johannes  Muller, 
suggested  even  by  Plato. 

When  Miller  postulates  in  the  famous  laws  which 
bear  hi^  name  qualitatively  different  changes  in  state  in 
each  variety  of  sensory  nerve,  changes  which  for  different 


8  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

stimuli  are  of  the  same  kind  in  the  same  nerve,  this  is 
not  at  all  synonymous  with  saying:  to  equal  amounts  of 
energy  equal  reactions. 

At  different  times  and  under  different  conditions  we 
react  differently  to  the  same  amount  of  energy,  and 
conversely.  Stimuli  carrying  an  amount  of  energy  which 
normally  is  not  perceived  can,  as  in  strychnine  poisoning, 
bring  about  most  powerful  effects.  The  selective  be- 
havior of  the  nervous  end-organs  must  also  be  attributed 
to  differences  in  the  stimuli  received,  which  are  more 
than  simple  quantitative  differences  in  energy.  How 
great  is  the  difference  between  our  sensations  of  noise 
and  of  music !  and  yet  the  value  of  the  transmitted  energy 
in  the  two  cases  may  be  the  same. 

It  would  be  an  easy  matter  to  increase  the  number 
of  striking  examples  indefinitely.  They  all  lead  to  the 
conclusion  that  the  quality  of  a  natural  stimulus  plays 
an  important  role,  as  well  as  the  amount  of  its  energy. 
Muller  himself  is  inclined  to  make  a  qualitative  dis- 
tinction between  impulses  when  he  speaks  of  homogeneous 
and  heterogeneous  stimulation  of  a  sense-organ.  After 
all  that  has  been  said  the  assertion  seems  justified  that 
the  new  energetic  world  conception  will  prove  to  be 
scarcely  less  poor  than  the  mechanical.  Did  we  wish  to 
go  deeper  we  should  have  to  call  the  former  a  purely 
mechanical  one. 

If  with  this  we  have  to  regard  as  a  failure  the  attempt 
to  solve  from  the  standpoint  of  energetics  du  Bois- 
Reymond's  famous  riddle  of  the  universe,  then  of  what 
value  are  the  laws  governing  energy  in  the  investigation  of 
biological  problems? 

If  we  know  from  experience  or  if  this  leads  us  to  assume 


ON  PHYSICO-CHEMICAL   METHODS  AND  PROBLEMS        9 

that  two  processes  influence  each  other  in  the  way,  for 
example,  that  pressure  affects  the  freezing-point  of  water 
or  the  electric  current  a  magnet,  the  degree  of  this  action 
upon  each  other  can  be  directly  deduced  from  the  laws 
of  energy. 

If  in  the  explanation  of  a  phenomenon  we  build  it 
up  out  of  the  elements  a,b,c,d  .  .  .  ,  then  these  elementary 
processes  correspond  with  a  group  of  transformations  in 
energy  which  we  will  designate  by  a,  /?,  y,  d  .  .  .  The 
principle  of  energetics  states  that  the  sum  of  «+/?  +  /'  + 
d  .  .  .  must  be  constant.  The  attempted  analysis  of  the 
phenomenon  into  a,  b,  c,  d  is  possible  only  when  it  sat- 
isfies at  the  same  time,  under  the  most  varied  circum- 
stances, the  above  condition.  The  Mayer- Joule  law 
contains  no  more  than  this.  But  while  it  itself  therefore 
gives  no  positive  or  complete  insight  into  a  phenomenon, 
it  nevertheless  renders  possible  the  exclusion  of  a  whole 
series  of  false  interpretations  of  our  observations.  It 
constitutes,  therefore,  an  indispensable  and  excellent  con- 
trol of  our  suppositions. 

This  control  of  our  conceptions  through  the  Mayer- 
Joule  law  may  be  of  two  kinds.  In  the  one  case  it  will 
be  able  to  prove  that  our  assumption  is  wrong,  in  another 
that  it  is  incomplete.  In  so  far  as  it  points  out  in  the 
latter  case  an  as  yet  undiscovered  condition  it  seems 
under  these  circumstances  to  lead  directly  to  the  dis- 
covery of  new  facts. 

But  even  under  these  conditions  we  learn  from  the 
law  of  energy  only  that  something  is  to  be  sought  or  to 
be  discovered.  What  this  really  is,  or  what  the  nature 
of  the  fact  that  is  to  be  discovered  is,  can  never  be  learned 
except  through  special  investigation.     We    may  say   in 


Id  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

consequence  that  the  energetic  principle  has  really  only 
a  formal  significance,  and  can  tell  us  nothing  regarding 
the  quality  of  the  process.  This  is  apparent  from  its  very 
nature,  namely,  that  of  combining  equivalents.  With 
what  the  numerical  equivalence  corresponds  in  any  given 
case,  of  this  the  law  tells  us  nothing;  just  as  little  as 
we  know  from  the  weight  of  an  amount  of  gold  what 
kind  of  money  it  is,  whether  francs,  marks,  or  guldens. 

The  law  of  the  conservation  of  energy  could  not  help 
but  have  from  its  very  beginning  an  overwhelming 
effect  upon  every  investigator,  not  only  because  of 
its  great  simplicity  but  also  because  of  its  unlimited 
tenability  in  all  subjects. 

It  can  seem  little  strange,  therefore,  that  its  heuristic 
value  has  often  been  overestimated.  It  is  certainly  going 
too  far  when,  for  example,  a  recognized  medical  historian 
says  of  the  law,  "The  discovery  of  the  law  of  the  con- 
servation of  energy  has  contributed  no  mean  amount 
toward  disproving  the  vitalistic  theory,  that  belief  in  a 
peculiar  vital  force,  and  toward  proving  that  the  laws 
of  physics  and  chemistry  suffice  to  explain  all  biological 
and  pathological  phenomena." 

The  darkness  which  envelops  life  phenomena  cannot 
be  illuminated  through  any  principle  of  mechanics. 
For  the  time  being,  therefore,  the  belief  in  a  vital  force 
must  needs  continue  to  exist.  As  in  the  case  of  the 
other  "forces"  it  too  has  had  to  bow  to  the  law  of  energy, 
but  its  death-blow  will  be  received  only  when  our  knowl- 
edge of  natural  phenomena  will  have  attained  a  higher 
development  than  at  present. 

We  have  in   the   preceding   paragraphs   tried   to   go 


ON  PHYSICO-CHEMICAL   METHODS  AND  PROBLEMS.      II 

back  to  the  very  foundations  of  modern  chemistry  in 
order  to  obtain  a  conception  of  its  applicability  to  biological 
questions.  In  what  follows  an  attempt  will  be  made 
to  ascertain  the  value  of  physico-chemical  methods  in 
special  questions  in  medicine.  A  division  of  our  sub- 
ject might  follow  either  one  of  two  schemes.  According 
to  the  first  the  division  would  follow  that  current  in 
physical  chemistry.  A  second,  however,  which  seems 
better  adapted  to  our  purposes,  takes  into  consideration 
the  medical  problems  that  have  made  use  of  the  new 
methods. 

We  can  readily  distinguish  between  two  fields  of 
biochemical  research.  One  in  which  dead  material  is 
studied  and  through  a  discovery  of  the  structure  of 
chemical  substances,  such  as  the  proteins  and  carbo- 
hydrates, an  explanation  of  their  biological  significance 
is  sought;  and  a  second  which  approaches  the  tissues 
and  their  functions  directly  and  endeavors  to  unveil 
their  secret  vital  activity  through  an  investigation  of 
their  constituents  and  products.  Often  investigations 
that  utilize  more  or  less  strictly  the  living  organism  have 
a  knowledge  of  the  results  obtained  in  the  first  field  upon 
which  to  base  their  work.  True  as  seems  to  be  the 
assertion  that  a  broad  chasm  exists  between  the  great 
group  of  proteins  and  living  protoplasm,  equally  true 
is  it  that  a  bridge  leads  across  this  chasm,  even  though 
investigation  has  not  yet  succeeded  in  recognizing  the 
nature  of  this  connection.  We  may  therefore  expect  that 
in  the  chemical  and  physical  reactions  of  the  proteins 
there  exist  even  now  many  of  the  elements  of  physiological 
and  pathological  reactions.  In  fact  this  expectation 
has    been    fulfilled    in    great    measure    more    especially 


12  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

through  a  utilization  of  the  methods  of  physical  chem- 
istry. 

The  studies  of  Hofmeister  on  the  protein -precipitating 
power  of  salts  have  shown  that  these  arrange  themselves 
in  the  same  order  as  they  do  when  arranged  according 
to  their  diuretic  or  cathartic  action. 

In  a  study  of  the  condition  of  swelling  which  I  pub- 
lished some  time  ago  a  large  number  of  biological  rela- 
tions were  found.  Analogies  exist,  for  example,  between 
the  absorption  of  water  by  substances  capable  of  swelling 
and  the  absorption  of  water  by  the  living  organism; 
and  the  velocity  of  swelling  and  the  time  of  a  muscle 
contraction  are  about  the  same.  A  continuation  of 
these  experiments  along  the  line  of  changes  in  the  physical 
state  of  the  proteins  has  led  to  results  whose  significance 
also  extends  beyond  that  for  the  dead  material  itself. 

As  is  well  known  the  proteins  suffer  when  subjected  to 
heat  a  change  in  state,  a  so-called  coagulation,  which,  gen- 
erally speaking,  is  not  reversible.  The  coagulation  point, 
that  is  the  temperature  at  which  this  change  takes  place, 
is,  among  other  things,  dependent  to  a  large  extent  upon 
the  presence  of  neutral  salts.  If  we  employ  the  neutral 
salts  in  the  form  of  equimolecular  solutions,  we  can 
compare  their  effects  on  the  coagulation-point,  which 
may  vary  between  more  than  fifteen  degrees  centigrade. 
If  now  we  plot  the  concentrations  upon  the  abscissas,  the 
corresponding  coagulation  temperatures  upon  the  ordi- 
nates,  we  obtain  curves  which  give  a  general  survey  of 
the  laws  governing  the  process.  From  these  we  learn 
that  with  solutions  of  a  medium  concentration,  the 
order  in  which  the  different  salts  follow  each  other  when 
arranged  according  to  their  different  acids  is  independent 


ON  PHYSICO-CHEMICAL    METHODS   AND   PROM. EMS.      1 3 

of  the  base  common  to  all  of  them.  If  the  salts  are 
arranged  according  to  their  bases,  then  they  follow  each 
other  in  a  certain  order  which  is  independent  of  the 
acid  common  to  all. 

The  effect  of  ;i  salt  upon  the  coagulation  temperature 
is  therefore  made  up  of  two  components  the  effect  of 
the  acid  and  the  effect  of  the  basic  parts.  We  call  this  an 
additive  ion  effect. 

The  remarkable  phenomena  observed  when  two  salts 
Si  and  S-2  together  affect  the  coagulation-point  give  us 
a  deeper  insight  into  the  important  biological  relations 
existing  between  proteins  and  salts. 

If  in  a  protein-salt  mixture  to  which  a  definite  amount 
of  So  has  been  added  we  allow  the  salt  Si  to  vary  in 
concentration,  while  in  a  second  series  of  experiments 
we  repeat  this  but  use  a  different  amount  of  So,  etc.,  we 
obtain  a  group  of  curves.  A  second  series  of  curves 
are  obtained  by  using  constant  amounts  of  Si  and  varying 
amounts  of  So-  In  this  way  we  obtain  two  groups  of 
curves  which  illustrate  very  well  the  mutual  effects 
of  two  salts  upon  protein  coagulation.  These  curves 
show  in  a  very  remarkable  way  points  at  which  they 
cross  each  other,  in  other  words  a  constancy  in  the 
coagulation-point  as  soon  as  certain  quantitative  rela- 
tions exist  between  the  two  salts.  When  this  is  attained 
a  change  in  the  concentration  of  one  of  the  salts  which 
a!  other  times  would  bring  about  a  change  in  the  coagu- 
lation temperature  remains  entirely  without  effect  even 
when  the  amount  of  the  change  is  four  or  five  times  as 
great. 

A  point  at  which  the  curves  cut  each  other  may  be 
shown  also  between  the  combination  curve  Si+So  and 


14  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

the  pure  Si  curve.  In  other  words  in  a  definite  salt- 
protein  mixture  the  addition  of  an  indefinite  amount 
of  another  salt  does  not  change  the  coagulation- 
point. 

These  experiments,  which  are  given  here  only  in  part, 
seem  to  show  for  the  first  time  that  compounds  of  a  certain 
stability  are  formed  when  salts  are  mixed  with  pro- 
teins. 

The  additive  ion  effects  of  the  salts  show  also  a  depen- 
dence upon  certain  quantitative  relations.  We  must 
probably  attribute  this  to  an  affinity  between  salt  and 
protein  which,  as  indicated  by  other  observations,  is 
of  such  a  character  that  the  metallic  ion  and  the  acid 
ion  of  a  salt  unite  with  different,  asymmetric  parts  of 
the  protein  molecule. 

An  investigation  of  the  conditions  determining  the 
solubility  of  egg  globulin  has  shown  that  this  is  dependent 
upon  the  presence  of  ionized  compounds.  In  even  a 
highly  concentrated  solution  of  dextrose  or  urea,  in  other 
words  substances  which  do  not  dissociate  into  ions, 
globulin  is  precipitated  in  the  same  way  as  in  the  almost 
entirely  non-ionized  water. 

We  may  point  out  in  passing  the  biological  significance 
of  these  facts  which  show  the  importance  of  the  mineral 
constitutents  of  the  organism  in  a  new  light. 

There  can  be  little  doubt  that  ion-protein  compounds 
are  present  in  the  animal  organism,  in  fact  we  have 
every  reason  for  believing  that  all  protein  constituents  of 
the  protoplasm  enter  into  the  composition  of  this  sub- 
stance only  in  combination  with  ions. 

As  shown  by  numerous  observations,  the  salts  are 
held  fast  in  the  organism  with  great  force.     This  affinity, 


ON  PHYSICO-CHEMICAL    METHODS   AND  PROBLEMS.      15 

which  until  now  could  scarcely  be  explained,  is  an  analogue 
of  the  affinity  existing  between  salts  and  proteins  as  dis- 
cussed above. 

The  way  in  which  water  and  the  way  in  which  salt  are 
united  with  the  colloids  have  many  things  in  common, 
for  the  water  and  salt  mutually  affect  each  other  in  the 
organism,  and  each  of  the  two  is  maintained  at  as  constant 
a  value  as  possible.  If  we  allow  a  swollen  colloid  to 
desiccate  in  an  atmosphere  which  is  kept  permanently 
dry,  we  find  that  it  loses  water  in  a  way  analogous  to 
that  in  which  a  protein-salt  mixture  loses  salt  when 
dialyzed  against  running  water.  In  either  case  some 
water  or  some  salt  remains  behind  which  can  be  removed 
only  with  the  greatest  difficulty  if  it  can  be  removed 
at  all.  The  ion-protein  compounds  show  a  considerable 
stability  toward  conditions  influencing  their  state  of 
aggregation  in  yet  another  way.  The  presence  of  neutral 
salts,  for  example,  inhibits  the  effect  of  an  acid  or  an  alkali 
upon  the  dissolved  globulin,  while  non-ionized  substances 
do  not  do  this. 

We  must  therefore  look  upon  the  ion-protein  compounds 
as  being  of  importance  in  the  animal  body  through 
their  ability  to  decrease  its  sensitiveness  toward  changes 
in  concentration,  changes  in  temperature,  and  changes 
in  alkalinity. 

Through  the  decomposition  of  the  large  protein  mole- 
cules and  certain  carbohydrates  there  are  produced 
during  metabolism  substances  having  a  low  molecular 
weight  which  in  many  ways  have  characteristics  in 
common  with  those  of  the  salts, — such,  for  example, 
as  urea  or  sugar.  All  these  substances  are  either  not 
at  all  or  only  slightly  ionized  in  water.     They  are  there- 


1 6  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

fore  not  able  to  replace  the  salts  which  in  dilute  solution 
are  almost  completely  ionized. 

It  is  not  the  salts  but  the  ions  of  the  salts  that  are  essen- 
tial to  the  organism. 

Our  belief  that  many  reactions  of  living  matter  can 
be  traced  back  to  the  properties  of  the  dead  ground- 
substance  itself  seems  to  be  true  not  alone  of  the  proteins 
and  their  closely  related  bodies. 

Emil  Fischer  has  been  able  to  show,  for  example,  that 
the  fact  that  enzymes  or  living  organisms  split  certain 
kinds  of  sugars  more  easily  than  others  is  dependent 
upon  their  structural  peculiarities,  and  has  assumed  the 
existence  of  a  peculiar,  stereochemical  relation'  between 
the  reacting  substances. 

A  remarkable  similarity  between  the  reactions  in  dead 
and  in  living  matter  has  also  been  proven  to  exist  for  the 
fats.  If  we  allow  two  immiscible  liquids,  such  as  oil 
and  water,  to  compete  for  a  substance  soluble  in  both, 
the  amounts  of  this  substance  dissolved  in  the  two  solvents 
bear  a  definite  proportion  to  each  other.  Meyer  and 
his  pupil  Baum  have  studied  a  long  series  of  narcotics 
with  reference  to  their  distribution  coefficient  in  the 
above  mixture,  and  have  been  able  to  point  out  a  far- 
reaching  parallelism  between  the  distribution  coefficient 
of  a  substance  and  its  narcotic  effect.  This  observation 
has  led  Meyer  to  an  interesting  theory  of  narcosis, 
based  upon  the  difference  in  the  distribution  of  the  active 
substances  between  the  watery  tissue  fluids  and  the  fat- 
like constituents  of  nerve  tissue. 

We  will  now  leave  the  field  of  more  or  less  indirect 
biochemical  investigation  and,  even  though  but  hastily, 
consider  the  results  which  have  been  obtained  through 


ON  PHYSICO-CHEMICAL   METHODS   AND  PROBLEMS.      H 

a  direct  application  of  the  new  methods  to  changes  which 

go  on  in  the  organism.  These  belong  more  or  less  in  the 
field  of  special  physiology,  while  the  foregoing  fall  more 
naturally  into  the  territory  of  general  physiology. 

We  have  to  deal  in  what  follows  almost  entirely  with 
the  principles  of  the  modern  theory  of  solution,  of  which 
extensive  use  is  made  in  the  explanation  of  phenomena 
of  absorption  and  secretion. 

We  must  consider  it  a  great  advance  that  we  now  know 
that  almost  all  relations  existing  between  the  red  blood- 
corpuscles  and  the  plasma  can  be  explained  by  the  laws 
which  govern  any  solution.  The  credit  of  having  recog- 
nized this  fact  belongs  chiefly  to  Hamburger  and  Kg-ppe. 
These  investigations,  it  seems  to  me,  are  the  first  to 
conclusively  do  away  with  any  higher  life  in  the  blood. 
What  appears  as  life  in  the  blood  is  only  a  reflection  of 
those  true  vital  processes  which  go  on  in  the  tissues.  All 
known  changes  which  take  place  in  the  circulating  blood 
(with  the  exception  of  the  white  blood-corpuscles)  are 
passive  physico-chemical  reactions,  and  are  in  consequence 
independent  of  nervous  influence. 

Of  special  physiological  and  pathological  interest  are 
the  efforts  to  explain  the  activities  of  the  kidneys  from 
these  new  points  of  view.  The  starting-point  of  these  is 
furnished  by  a  paper  of  Dreser,  in  which  this  author 
develops  for  the  first  time  the  conception  of  the  osmotic 
work  of  the  kidneys  and  calculates  this  in  mechanical 
work-units.  A  detailed  study  of  this  fundamental  con- 
ception is  desirable,  since  in  its  original  form  it  is  neither 
entirely  clear  nor  complete. 

We  can  determine  the  number  of  particles  present  in 
the  unit  volume  of  a  solution,  the  so-called  molecular 


1 8  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

concentration,  either  through  a  determination  of  the 
osmotic  pressure — the  attraction  between  dissolved  par- 
ticles and  solvents — or  the  change  in  the  freezing-point 
or  boiling-point  of  the  solution. 

All  these  values  are  related  in  a  simple  way  and  are 
independent  of  the  nature  of  the  dissolved  substances. 
If  we  wish  to  increase  the  concentration  of  an  aqueous 
solution  we  must  remove  a  part  of  its  water.  It  is 
immaterial  whether  we  do  this  through  evaporation 
freezing,  or  expression  of  the  water  through  a  membrane 
impermeable  to  the  dissolved  substances,  or  whether  this 
process  takes  place  in  the  kidneys:  in  every  case  the 
amount  of  work  required  must,  according  to  the  laws  of 
energy,  be  the  same.  The  amount  of  this  work  is  deter- 
mined solely  by  the  original  concentration  and  the  change 
in  concentration  finally  attained.  With  these  facts  in 
mind,  we  will  try  to  formulate  the  conception  of  renal 
work  more  clearly. 

While  the  molecular  concentration  or  the  freezing- 
point  of  normal  blood  has  an  almost  constant  value,  that 
of  the  urine  varies  within  wide  limits.  Our  kidneys  are 
able  to  furnish  a  secretion  the  freezing-point  of  which 
may  be  higher  or  lower  than  that  of  the  blood.  For  the 
sake  of  simplicity,  it  may  be  well  to  consider  these  two 
possibilities  separately. 

If  the  kidneys  furnish  a  urine  having  a  higher  freezing- 
point  than  that  of  the  blood,  then  their  entire  activity 
consists  in  the  mere  preparation  of  a  dilute  urine,  and 
these  organs  do  their  osmotic  work  by  expressing  from  the 
more  highly  concentrated  blood  a  certain  amount  of  water. 
During  all  this  time  the  osmotic  pressure  of  the  blood  is 
Of  course  kept  at  its  original  height  through  the  tissues. 


ON  PHYSICO-CHEMICAL   METHODS   AND   PROBLEMS.      >9 

The  amount  of  water  given  off  can  be  readily  calcu 
lated:    it  is  the  amount  which  must  be  separated  from 
the  urine  in  order  to  change  this  into  a  liquid  having  the 
high  molecular  concentration  of  the  blood. 

The  calculation  of  the  work  necessary  to  accomplish 
this  is,  however,  not  as  simple  as  Dreser  believes,  since 
through  the  transport  of  the  water  from  the  blood  to  the 
urine  the  concentration  of  the  latter  is  steadily  altered, 
a  fact  which  this  author  has  not  taken  into  consideration. 

We  will  look  upon  the  amount  of  work  necessary  for 
this  purpose,  which  can  be  determined  mathematically 
as  a  measure  of  the  watcr-sccretory  function  of  the  kidnevs. 

The  converse  of  the  above  would  exist  when  the  kidney 
has  to  prepare,  from  a  liquid  having  the  osmotic  pressure 
of  the  blood,  one  having  a  molecular  concentration 
greater  than  the  blood.  Under  these  conditions  we 
should  have  to  add  a  certain  amount  of  water  to  the  urine 
in  order  to  make  its  osmotic  pressure  equal  to  that  of  the 
blood.  While  in  the  first  case,  therefore,  the  kidnevs 
have  to  express  water  from  the  blood,  this  time  they 
have  to  express  it  from  the  urine  and  return  it  to  the 
blood. 

The  work  corresponding  to  this,  which  has  been  cor- 
rectly determined  by  Dreser,  we  will  have  to  regard  as 
a  measure  of  the  water-absorption  activity  of  the  kidnevs. 

As  we  know  from  numerous  facts,  this  double  function 
of  the  kidney  is  performed  by  two  difTerent  parts  of  the 
organ.  While  the  glomeruli  probably  secrete  the  water 
of  the  urine,  the  uriniferous  tubules  have  an  antagonistic 
function. 

The  urine  which  we  arc  able  to  examine  has  already 
been  subjected  to  both  kinds  of  work.     We  are  able  to 


iO  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

determine  from  it,  by  freezing-point  determinations,  only 
the  difference  between  these  two  values,  while  the  kidney 
has  in  reality  performed  the  sum  of  the  two.  All  the 
measurements  of  osmotic  renal  activity  made  by  Dresee. 
do  not  take  this  important  fact  into  consideration.  Failure 
to  consider  it  must  of  necessity  lead  to  radically  incorrect 
conclusions. 

The  normal  human  being  usually  secretes  a  urine  the 
freezing-point  of  which  is  lower  than  that  of  the  blood, 
because  its  molecular  concentration  is  greater.  By  con- 
suming much  water  we  are,  however,  able  to  raise  the 
freezing-point  of  our  urine,  and  it  would  not  be  difficult 
to  so  regulate  by  artificial  means  the  amount  of  water 
taken  up  by  the  organism  that  the  freezing-point  of  urine 
and  blood  would  be  the  same.  If  now  we  base  our  cal- 
culation of  renal  work  upon  the  difference  between  the 
freezing-point  of  the  blood  and  that  of  the  urine, — a 
difference  which  under  these  circumstances  would  be 
zero,— then  we  would  be  compelled  to  conclude  that  the 
secretion  of  a  urine  equimolecular  with  that  of  the  blood 
had  been  accomplished  without  work,  while  as  an  actual 
matter  of  fact  it  may  have  demanded  a  great  deal  of 
work.  For  after  what  has  been  said  it  is  clear  that  the 
osmotic  work  of  water  secretion  and  the  osmotic  work  of 
water  absorption  by  the  kidneys  equal  each  other  in  this 
case. 

A  statement  which  is  found  in  various  articles  and  which 
threatens  to  be  adopted  by  text-books,  that  the  work  per- 
formed by  the  kidneys  in  twenty-four  hours  normally 
varies  between  70  and  240  kilogrammeters,  has  therefore 
no  real  value.  After  what  has  been  said  it  will  not  seem 
strange  that  the  attempts  to  utilize  for  diagnostic  pur- 


ON  PHYSICO-CHEMICAL   METHODS  AND  PROBLEMS       2 1 

poses  the  work  of  the  kidneys  as  determined  in  this  w;iy 
have  failed. 

It  seems  to  me  that  still  another  point  should  be  noted. 
It  is  readily  apparent  when  one  studies  the  papers  that 
have  followed  Dreser's  initiative  that  the  method  of 
measuring  the  work  of  the  kidneys  as  criticised  above 
has  been  regarded  as  giving  the  value  of  the  total  work 
done.  At  the-  best,  however,  the  method  determines 
only  that  portion  of  the  work  which  is  necessary  to  bring 
about  the  secretion  of  the  water  of  the  urine.  For  our 
urine  does  not  represent  a  concentrated  or  a  diluted 
blood,  but  contains,  as  we  know,  the  constituents  of  the 
blood  in  different  concentrations,  even  when  we  disregard 
the  osmotically  inactive  substances  (albumin). 

If  we  imagine  a  certain  amount  of  urine  having  the 
same  freezing-point  as  the  blood,  separated  from  this 
by  a  thin  permeable  membrane,  and  the  blood  kept  in 
circulation  and  maintaining  its  original  composition  as 
in  the  body,  an  interchange  between  the  diffusible  con- 
stituents of  the  urine  and  those  of  the  blood  takes  place 
until  the  amount  of  these  is  the  same  on  both  sides  of  the 
membrane.  We  will  call  such  an  interchange  a  molecular 
interchange,  as  does  Koranyi,  because  the  molecular 
concentration  of  the  two  fluids  remains  the  same  through- 
out the  experiment.  As  we  do  not  have  to  do  in  this 
case  with  differences  in  osmotic  pressure,  the  external 
work  is  zero.  But  a  certain  amount  of  internal  work 
is  performed,  the  direction  of  which  can  also  be  deter- 
mined. For  substances  migrate  from  regions  having  a 
higher  concentration  to  those  having  a  lower  one,  through 
which  a  certain  amount  of  osmotic  work  becomes  free 
for  each  of  the  substances.     The  sum  of  all  these  different 


22  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

amounts  of  diffusion  work  would  have  to  be  used  in  order 
to  separate  the  substances  again  and  to  bring  about  the 
original  differences.  This  work  must  also  be  done  by 
the  kidneys,  and  in  two  directions,  toward  the  urine  and 
toward  the  blood.  The  value  of  this  can  also  be  calcu- 
lated, a  subject  which  is,  however,  not  within  the  bounds 
of  this  paper.  We  may  call  this  the  selective  work  of  the 
kidneys. 

The  osmotic  work  of  the  kidneys  is  therefore  made 
up  of  three  components — the  osmotic  work  of  water 
secretion,  that  of  water  absorption,  and  that  of  selection. 

Dead  material,  such  as  gelatine  plates,  may  also  show 
a  power  of  selection.  For  a  recognition  of  this  important 
fact  we  are  indebted  to  Hofmeister  and  his  pupil  Spiro. 
The  latter  has  elucidated  these  phenomena  through 
physico-chemical  principles. 

While,  however,  a  gelatine  plate  that  has  absorbed 
a  salt  or  a  dye  remains  in  equilibrium  with  its  surround- 
ings and  is  not  capable  of  any  further  selective  activity, 
the  phenomena  observed  in  the  kidney  are  of  a  dynamic 
nature. 

The  selective  function  of  the  kidney  is  an  uninterrupted 
process,  maintained  through  the  active  metabolism  of  its 
living  substance. 

It  is  not  possible  to  mention  here  all  the  other  beautiful 
applications  that  have  been  made  of  physical  chemistry 
to  questions  in  physiology  and  pathology.  Many  im- 
portant advances  besides  those  already  noted  might  be 
brought  up  here.  Pharmacodynamics  may  also  expect 
great  changes  through  use  of  the  new  theories,  as  may 
be  concluded  from  the  attempts  which  are  already  being 
made  to  introduce  these  new  methods  into  this  science. 


<:/  LLS  AND   TISSUES.  *3 

In  fact,  no  branch  of  our  science  will  attempl  to  solve 
the  new  questions  presented  to  ii  without  rich  results. 

1  have  arrived  at  the  end  of  my  paper,  the  purpose  of 
which  was  to  test  the  value  of  the  methods  of  physical 
chemistry  in  questions  of  medicine.  Unquestionably 
they  enlarge  that  territory  which  the  organic  and  the 
inorganic  world  have  in  common.  The  last  barriers 
between  the  two  cannot  as  yet  be  broken  down,  how- 
ever, through  the  increase  in  our  means  of  investigation 
that  we  are  at  present  enjoying.  There  always  remains 
an  unsolved  portion,  the  kernel,  as  it  were,  of  vital 
phenomena. 

The  cause  of  the  final  failure  of  the  new  instruments 
can  rest  only  in  their  origin.  They  have  all  been  evolved 
from  the  study  of  lifeless  matter.  For  a  complete  under- 
standing of  the  living  the  words  of  a  great  physiologist 
will  probably  hold: 

"Life  can  perhaps  be  completely  understood  only  through 
life  ilsclj. " 

2.  The  General  Physical  Chemistry  of  the  Cells  and 
Tissues.* 

A  complete  and  ordered  understanding  of  all  the  func- 
tions of  living  matter,  independent  of  its  relation  to  a 
definite  organism  or  organ,  is  the  final  goal  of  general 
ph  ysiology.  Free  from  a  one-sided  overestimation  of  any 
one  system  of  investigation,  it  makes  use  not  only  of  the 
methods  peculiar  to  biology,  but  also  of  those  employed 
in  physics  and  chemistry.  The  methods  of  chemistry 
have  attained  a  special  importance  in  the  investigation 

*  From  Ergobnissc  der  Physiologie,  1903,  I,  ite  Abth.,  p.  1. 


24  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

of  the  metabolic  changes  that  take  place  in  living  matter. 
This  so-called  vegetative  physiology  has  been  greatly 
advanced  through  the  modern  development  of  theoretical 
or  physical  chemistry.  It  is  the  purpose  of  this  young 
and  rapidly  growing  branch  of  the  inorganic  sciences' to 
establish  the  general  laws  governing  chemical  changes. 
Through  the  stupendous  theoretical  and  experimental 
accomplishments  of  such  investigators  as  van't  Hoff, 
Arrhenius,  Gibbs,  Hittorf,  Kohlrausch,  Ostwald, 
Nernst,  and  Planck,  our  understanding  in  this  direction 
has  within  a  comparatively  short  time  been  incredibly 
increased  and  deepened.  As  in  every  great  development 
in  the  exact  sciences,  physiology  may  in  this  case  also 
expect  to  be  enriched  in  no  small  way,  and  though  it  to- 
day stands  only  at  the  beginning  of  this  wonderful  fertil- 
ization, the  number  of  workers  along  special  and  general 
subjects  in  physiology  is  daily  increasing.  In  fact,  in 
the  realm  of  general  physiology  the  physico-chemical 
method  of  looking  at  things  has  been  the  first  to  make 
it  possible  to  ask  many  questions  in  a  general  way  and 
to  answer  them  according  to  the  present  status  of  physico- 
chemical  investigation.  New  analogies  and  transitions 
between  phenomena  in  living  and  in  dead  matter  have 
been  discovered;  and  it  has  often  proved  no  small  task 
to  discover  that  side  of  a  phenomenon  which  charac- 
terizes it  as  a  specifically  biological  one. 

Important  as  many  of  the  advances  that  have  been 
made  may  seem,  closer  inspection  shows  that  even  at 
the  best  we  are  only  beginning  to  solve  the  questions  before 
us. 

The  development  brought  about  through  the  seeds  of 
physical  chemistry  has  as  yet  not  led  to  an  equilibrium 


CELLS  AND   TISSUES.  25 

between  our  imagination  and  fact,  due  in  part  to  a  lack 
of  chemical  data  of  biological  importance,  in  part  to  a 
laek  of  that  theoretical  foundation  necessary  for  spe<  ial 
questions  in  biology.  For  this  reason  the  following 
fragments  of  a  general  presentation  of  the  physical 
chemistry  of  the  cells  and  tissues  cannot  claim  to  In- 
complete or  to  give  a  satisfactory  account  of  facts  to 
which  nothing  more  will  ever  be  added.  It  must  suffice 
if  the  great  importance  of  physical  chemistry  in  general 
physiology  is  rendered  apparent. 


All  living  matter  is  made  up  of  colloidal  and  crystal- 
loidal  material,  and  there  exists  no  life  process  that  is 
not  accompanied  by  changes  in  the  colloidal  and  crystal- 
loidal  substances.  And  the  physico-chemical  laws  which 
govern  the  crystalloids  and  the  colloids  reappear  in  the 
numerous  properties  of  living  matter. 

The  colloids  have  for  the  most  part  a  high  molecular 
weight,  diffuse  only  with  the  greatest  difficulty,  and  do 
not  pass  through  animal  membranes.  Solutions  of  col- 
loids have  a  scarcely  measurable  osmotic  pressure,  and 
have  in  consequence  little  effect  in  raising  the  boiling- 
point  or  depressing  the  freezing-point.  They  do  not  con- 
duct the  electric  current,  yet  they  move,  for  the  most  part, 
in  an  electric  current. 

The  crystalloids  diffuse  easily  and  pass  readily  through 
animal  membranes.  Their  molecular  weight  is  low, 
while  their  affinity  for  water,  as  measured  by  an  in- 
crease in  the  boiling  point  or  a  depression  of  the  freezing- 
point  of  their  solutions,  is  very  great.     The  crystalloids 


26  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

are  divisible  into  two  groups — the  electrolytes,  which  in 
(aqueous)  solution  conduct  the  electric  current,  and  the 
non-electrolytes,  which  do  not.  To  the  first  class  belong 
the  salts,  acids,  and  bases;  to  the  latter  most  of  the 
organic  substances,  such  as  urea  and  sugar. 

Between  the  two  great  groups  of  colloids  and  crystal- 
loids there  exists  no  sharp  line,  for  we  are  acquainted 
with  "  half -colloids, "  which  stand  midway  between  these 
extremes.  But  because  of  the  typical  differences  existing 
between  the  extremes  of  the  whole  series,  differences 
which  all  substances  show  more  or  less  perfectly,  this 
division  into  colloids  and  crystalloids  is  nevertheless  of 
great  value. 

The  colloids  exist  in  two  states,  a  liquid  and  a  solid 
state.  In  the  liquid  state  they  are  known  as  sols  (Gra- 
ham), in  contrast  to  the  solid  state,  in  which  they  appear 
as  dry,  swollen,  coagulated  (through  heat  or  ferments), 
or  precipitated  (for  example,  through  electrolytes)  masses, 
which  are  known  as  gels.  A  question  that  arises  at  once 
is,  Do  the  colloids  of  living  matter  exist  in  the  sol  or  in 
the  gel  state  ? 

Protoplasm  possesses  properties  which  are  character- 
istic, generally  speaking,  of  both  solid  and  liquid  sub- 
stances. This  peculiarity  of  living  matter  has  given  rise 
to  great  discussions  between  the  believers  in  the  solid 
and  those  in  the  fluid  state  of  aggregation  of  protoplasm. 
The  ability  to  stand  alone — in  other  words,  a  relative 
independence  in  form,  which  often  expresses  itself  in  the 
existence  of  characteristic  cell  forms — corresponds  with 
the  properties  of  the  solid  state,  while  an  argument  for 
the  liquid  state  of  protoplasm  is  readily  found  in  the 
general  and  necessary  condition  that  chemical  reactions 


CELLS  AND   TISSUES.  27 

must  be  able  to  take  place  within  the  cell  and  often  with 
greal  \  elo<  Ity. 

In  those  cases  in  which  changes  in  the  shape  of  the 
protoplasm  under  investigation  can  be  easily  explained 
through  the  assumption  of  the  existence  of  a  surface 
tension,  there  seems  to  be  no  reason  for  doubting  the 
fluid  nature  of  the  protoplasm,  for  surface  tension  is 
ordinarily  looked  upon  as  a  dependable  criterion  of  the 
liquid  state.  The  amoeba,  which  becomes  spherical  in 
a  state  of  rest  or  when  universally  excited,  or  forms 
pseudopodia  when  it  suffers  a  local  alteration  in  surface 
tension,  may  be  looked  upon  as  a  liquid  mass  as  long  as 
it  has  not  been  possible  to  demonstrate  in  it  a  noticeable 
displacement  elasticity  such  as  torsion.  To  prove  the 
existence  of  the  latter  by  suitable  experiment  has  never 
been  attempted,  so  far  as  I  know.  Since  the  discovery 
of  the  "amoeboid"  movements  of  oil  droplets  and  the 
careful  physical  analysis  of  this  phenomenon  by  Quincke, 
the  formation  of  pseudopodia  has  been  robbed  of  the 
characteristics  of  a  specific  life  phenomenon,  and  later 
investigators  have  shown  that  it  is  governed  in  all  its 
details  by  the  laws  of  surface  tension.  The  taking  up  of 
food  and  the  process  of  defecation  in  rhizopods  can 
also  be  easily  explained  in  this  way.  Rhumbler  could 
even  imitate  most  cleverly  with  drops  of  chloroform  and 
threads  of  -hellac  such  apparently  complicated  phenomena 
as  the  rolling  up  of  algae  threads  within  the  body  of 
Amoeba  verrucosa.  By  similar  methods  he  was  able  to 
imitate  in  a  most  surprising  way  the  formation  of  cases 
about  tcstaceans  by  rubbing  up  fine  quartz  or  glass  pow- 
der with  different  kinds  of  oils  jr  chloroform,  and 
dusting  this  into  dilute  alcohol  or  water.     E.  Albrecht, 


28  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

who  has  formulated  the  question  of  the  state  of  aggre- 
gation of  living  matter  in  both  a  penetrating  and  per- 
tinent way  and  has  attacked  it  with  the  armament  of 
modern  physico-chemical  research,  could  bring  about  a 
separation  of  droplets  within  the  contents  of  a  number  of 
cells  such  as  those  of  the  sea-urchin  and  of  the  kidney. 
Such  a  separation  is  dependent  upon  differences  in  sur- 
face tension,  such  as  can  exist  apparently  only  between 
fluids.  Even  before  him  Berthold  had  regarded  the 
normal  formation  of  granules  and  vacuoles  in  protoplasm 
as  a  separation  of  droplets.  Jensen  has  measured  the 
tensile  strength  of  the  pseudopodia  of  orbitolites  and 
has  found  that  it  about  corresponds  with  the  calculated 
surface  tension.  This  author  has  also  again  pushed  into 
the  foreground  the  surface-tension  properties  of  liquids 
as  a  means  of  explaining  many  mechanical  properties  of 
living  matter. 

In  spite  of  these  results,  which  are  all  of  them,  appar- 
ently, capable  of  only  one  interpretation,  a  generalization 
in  the  sense  that  all  living  substance  must  be  liquid  meets 
with  difficulties.  The  maintenance  and  the  individuality 
of  form  in  cases  in  which  no  supporting  framework  is 
demonstrable  would  have  to  be  attributed  by  the  believer 
in  the  liquid  state  of  protoplasm  to  currents  that  are 
able  to  hold  their  own  against  disturbing  forces.  What 
is  of  static  origin  in  the  solid  state  of  aggregation  needs 
here  a  dynamic  explanation  which  brings  with  it  the 
assumption  of  a  constant  expenditure  of  work.  Since 
an  inner  stabile  differentiation  is  impossible  in  a  liquid 
(for  even  the  finest  particles  of  matter  dissolved  or  sus- 
pended in  a  liquid  endeavor  with  great  force  to  become 
uniformly  distributed  throughout  the  whole),  the  assump- 


CELLS  4ND   TISSUES.  29 

tion  of  a  liquid  state  of  aggregation  for  protoplasm  meets 
in  many  cases  with  still  greater  difficulties  than  does  the 
assumption  of  a  solid  state.  While,  for  example,  all  the 
different  portions  of  the  cell  body  of  an  amoeba  show 

the  same  behavior,  in  that  any  element  within  the  pro- 
toplasmic  mass  may  become  a  surface  element,  and  con- 
versely;  in  other  words,  every  particle  is  equally  capable 
of  the  functions  of  assimilation,  stimulation,  and  move- 
ment, there  exist  peculiarities  in  many  of  the  more  highly 
developed  unicellular  organisms,  or  the  individual  cells 
of  higher  animals,  which  can  scarcely  be  interpreted 
otherwise  than  as  expressions  of  polarity.  Under  this 
heading  belong,  for  example,  the  fact  that  absorption  and 
secretion  take  place  predominantly  in  certain  directions, 
the  dependence  of  muscular  stimulation  upon  the  angle 
of  the  current  and  the  direction  of  the  muscular  fibrils, 
and  the  polarity  of  phenomena  of  regeneration  in  plants 
and  animals.  These  phenomena,  which  indicate  a  per- 
sistent inner  differentiation,  can  scarcely  be  explained 
without  the  assumption  of  a  solid  orientation  0}  the  par- 
ticles of  living  matter. 

A  way  out  of  this  dilemma,  of  which  the  details  con- 
stitute a  literature  that  cannot  be  entered  into  in  this 
paper,  is  rendered  possible  through  a  study  of  the  colloidal 
state. 

II. 

Those  gels  which  were  said  above-  to  be  swollen  or 
solidified  (for  example,  ordinary  gelatine  or  agar-agar) 
show  the  properties  of  both  solids  and  liquids  united  in 
one,  in  much  the  same  way  as  protoplasm.  They  are 
capable  of  existing  in  all  stales  of  aggregation,  varying 


30  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

from  the  solid  to  the  liquid,  depending  only  upon  the 
amount  of  water  they  have  absorbed.  Chemical  reactions 
may  take  place  anywhere  in  such  a  medium,  and  with 
almost  the  same  velocity  as  in  the  fluid  absorbed  by  the 
colloid  alone.  Such  a  jelly  does  not  take  up  any  other 
colloid  which  is  brought  in  contact  with  it  (differentiation 
between  different  membraneless  cells),  and  a  foreign 
colloid  imbedded  in  it  does  not  tend  to  spread  (intra- 
cellular differentiation).  Such  gels  undergo  most  deli- 
cately shaded  changes  in  state  even  without  changes  in 
temperature,  through  the  action  of  substances  which  are 
present  in  the  living  organism.  They  may  be  rendered 
more  solid  or  more  fluid,  without  suffering  a  change  in 
the  amount  of  water  which  they  hold,  through  the  action 
of  crystalloids,  and  also  through  the  action  of  certain 
enzymes  (partial  or  complete  peptonization). 

Such  solid  colloids  show  yet  other  properties  that 
have  been  used  as  potent  arguments  in  favor  of  the 
entirely  fluid  character  of  living  matter.  If  mercury 
globules  are  driven  under  pressure  through  a  capillary 
into  solidified  gelatine,  the  gelatine  closes  in  as  completely 
behind  the  rapidly  moving  globules  as  a  liquid  itself. 
The  separation  of  droplets  such  as  Albrecht  has  de- 
scribed in  protoplasm  is  also  possible  in  solidified  gelatine. 
In  the  fluid  state,  that  is  to  say,  above  the  solidification- 
point,  gelatine  is  precipitated  by  certain  electrolytes  such 
as  the  sulphates,  citrates,  and  tartrates  of  the  alkali 
metals.  As  can  be  proved  microscopically  and  mechan- 
ically, this  precipitation  is  a  separation  of  droplets — 
the  appearance  of  a  "phase"  richer  in  gelatine.  The 
precipitating  power  of  the  electrolytes  decreases  with  an 
increase  in  the  temperature,  that  is  to  say,  a  more  con- 


CELLS   AND    TISSUES.  31 

centrated  salt  solution  is  required  to  precipitate  gelatine 
at  a  higher  temperature  than  at  a  lower  one.  Corre- 
sponding with  this,  it  is  an  easy  matter  to  prepare  con- 
centrations in  which  a  precipitation  will  not  take  place 
until  a  temperature  below  that  at  which  gelatine  becomes 
solid  has  been  reached.  When  this  temperature  has 
been  reached  a  precipitate  is  produced,  this  time  also  in 
the  form  of  fine  droplets,  in  the  solid  and  originally 
entirely  clear  gelatine.  We  can  therefore  not  regard 
such  a  separation  of  droplets  as  an  undeniable  proof 
of  the  fluid  character  of  a  medium.  That,  however,  the 
application  of  the  theory  of  surface  tension  to  certain 
cellular  phenomena  may  be  of  great  service,  as  shown 
by  the  observations  of  Albrecht,  is  of  course  not  ques- 
tioned by  the  above  experiment.  Nor  does  anything  stand 
in  the  way  of  looking  upon  the  shrinkage  forms  of  thin 
solidified  gelatine  (Butschli,  Pauli)  in  alcohol,  am- 
monium sulphate  solution,  etc.,  as  expressions  of  sur- 
face tension.  In  fact,  the  similarity  is  very  great  between 
such  shrinkage  forms  and  the  shapes  of  suspended 
("schwerloser")  masses  of  oil  (cubes,  cylinders,  etc.)  in 
suitable  media,  as  described  by  Plateau.  The  diffi- 
culties that  are  encountered  in  endeavoring  to  explain, 
on  the  basis  of  the  solid  nature  of  protoplasm,  the 
unhindered  appearance  and  solution  of  crystals  without 
the  formation  of  holes,  do  not  exist  in  the  case  of 
gels,  as  experiment  has  taught.  Ludeking  has  been 
able  to  demonstrate  with  the  polarization  microscope  the 
appearance  of  ice  crystals  in  the  clear  substance  of  thin 
slices  of  deeply  cooled  (— i8°C.)  gelatine.  One  can 
also  notice  in  salt  gelatines  in  which  the  crystalloid,  such 
as  ammonium  chloride,  shows  a  great   fall   in   solubility 


32  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

with  a  decrease  in  the  temperature,  that  with  a  fall  in 
the  temperature  supersaturation  and  finally  crystallization 
of  the  salt  occurs  in  the  solid  gelatine,  and  that  when  the 
gelatine  is  warmed  once  more  the  crystals  disappear 
without  leaving  a  trace  of  their  existence  behind  them; 
and  all  this  without  a  change  in  the  state  of  aggregation 
of  the  colloid. 

A  study  of  gels  has  disclosed  yet  other  interesting 
analogies  with  living  matter.  Variations  in  the  degree 
of  swelling  or  in  the  volume  of  jellies  having  the  approx- 
imate size  of  body  cells  occur  with  a  velocity  the  mag- 
nitude of  which  corresponds  very  well  with  that  observed 
in  the  changes  in  volume  noticed  in  living  matter.  Solid 
colloids  also  manifest  very  extensively  a  group  of  phe- 
nomena— so-called  adsorption  phenomena — the  simplest 
laws  of  which  still  demand  much  study.  In  these 
phenomena  a  chief  role  is  played  by  great  surfaces  which 
load  themselves  (depending  upon  the  pressure,  tempera- 
ture, etc.),  often  very  rapidly,  with  different  substances. 
If  one  bears  in  mind  the  complicated  combination  exist- 
ing in  a  solidified  gel  between  the  colloid  and  its  absorbed 
liquid — the  water  seems  to  be  held  in  part  mechanically, 
in  part  in  combinations  varying  from  the  most  firm  to  the 
loosest,  which  renders  possible  true  liquid  and  solid 
solutions  in  addition  to  pure  adsorption — one  is  impressed 
with  the  great  variety  of  ways  in  which  substances  may 
be  taken  up  in  such  colloids.  In  this  way  a  great  selection 
in  the  substances  offered  them  is  rendered  possible,  as 
Hofmeister  and  Spiro  were  able  to  illustrate  with  biolog- 
ically instructive  examples  in  gelatine  and  agar-agar 
plates. 

Since  a  part  of  the  imbibition  fluid  may  be  mixed 


CELLS  AND    TISSUES.  33 

with  ether-soluble  substances — in  the  protoplasm  these 
are  such  as  cholesterin  and  lecithin,  or,  as  Overton 
calls  them  all,  lipoids — these  gels  arc  able  to  take  up 
substances  which  arc  not  soluble  in  water.  The  man- 
ner in  which  the  lipoids  are  held  by  the  cell  plasma, 
the  nature  of  which  is  still  unknown,  must  no  doubt  be 
governed,  according  to  our  newer  physico-chemical 
conceptions,  by  some  property  of  the  lipoids,  such  as 
their  solution  affinity.  According  to  the  extensive  investi- 
gations of  Overton,  the  ability  of  many  substances 
soluble  only  with  difficulty  in  water  to  enter  the  living 
cell  is  dependent  upon  their  solubility  in  the  lipoids. 

If  by  the  distribution  coefficient  of  a  substance  between 
two  solvents  we  understand  the  relation  between  the 
spacial  concentrations  which  exist  in  these  two  solvents 
after  equilibrium  has  been  established,  it  is  found  that 
the  distribution  coefficient  of  many  narcotics  between  oil 
and  water  determines  also  their  distribution  between 
medium  (such  as  blood  plasma)  and  cell  contents  (such 
as  the  lipoids  of  the  brain),  and  therefore  also  their  effect 
(Meyer,  Overton).  The  investigations  of  Frieden- 
thal  on  absorption  by  the  intestine  of  substances  insol- 
uble in  water  also  belong  under  this  heading,  which  is  of 
such  fundamental  importance  in  many  questions  in  physi- 
ology. Spiro  has  given  numerous  examples  of  the  gen- 
eral significance  of  the  distribution  law.  No  doubt  experi- 
ments carried  out  on  simple  models  would  bring  much 
light  into  this  field. 

After  what  has  been  said,  the  similarity  in  important 
physico-chemical  properties  between  living  matter  and 
certain  gels  must  be  looked  upon  as  an  extensive  one. 
Without  doubt  a  continued  investigation  of  the  colloid- 


34  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

is  destined  to  contribute  much  toward  an  understanding 
of  biological  problems. 

III. 

The  sols  also  play  an  eminent  part  in  life  processes. 
In  contrast  to  the  green  plants,  which,  according  to  well- 
known  cultural  experiments,  are  able  to  obtain  their 
nourishment  from  pure  crystalloidal  solutions,  animals 
are  dependent  upon  liquid  colloidal  food.  The  process 
of  digestion  serves  to  prepare  nutrient  sols  capable  of 
absorption,  and  fluid  colloids  are  mechanically  moved 
about  and  distributed  throughout  the  organism  to  the 
nourishing  tissue  fluids.  While  exerting  only  a  slight 
osmotic  pressure,  the  dissolved  colloids  are  nevertheless 
able,  through  their  inability  to  pass  through  animal 
membranes,  to  exert  a  resorptive  power,  which  through 
a  steady  change  in  the  osmotically  active  material,  as 
maintained  by  the  circulation,  finally  attains  significant 
proportions  (Okerblom). 

As  recent  investigations  have  shown,  the  sols  have 
several  important  properties  in  common  with  true  sus- 
pensions of  very  fine  particles.  The  most  important  of 
these  from  a  biological  standpoint  is  the  at  times  enormous 
surface  effect  of  the  colloidal  particles  contained  in  the 
solution.  Bredig,  who  rediscovered  the  well-known 
ferment-like  action  of  metallic  surfaces  in  the  enormously 
more  active  colloidal  solutions  of  metals,  and  investigated 
the  whole  subject  quantitatively,  has  attempted  to  explain 
the  importance  of  the  colloidal  condition  of  the  enzymes 
by  the  enormous  surface  effects  with  which  this  condition 
is  combined. 

The  free  surface  energy  and  the  osmotic  energy  seem 


CELLS  AND    TISSUES.  35 

in  many  way-  to  bear  a  reciprocal  relation  to  each  other 
in  the  cell.  The  analysis  of  the  colloidal  material 
decreases  the  former  while  it  increases  the  latter,  and 
conversely.  The  metabolic  changes  which  are  forever 
going  on  in  the  living  organ  compel  us  to  look  upon  life 
as  a  dynamic  process,  and  the  repeated  attempts  that 
have  been  made  to  comprehend  life  physico-chemically 
without  taking  this  fact  into  consideration  could  not  help 
but  seem  inadequate.  To  discover  the  right  connection 
between  this  metabolic  physiology  and  physical  chemistry 
is  among  the  most  important  of  the  problems  of  general 
vegetative  physiology. 

IV. 

The  biological  significance  of  the  crystalloids  has  until 
recently  been  the  main  object  of  research  with  the 
majority  of  those  investigators  who  have  made  use  of 
physico-chemical  methods  in  physiological  questions. 
Especially  has  use  been  made  of  the  theory  of  solutions. 
The  great  fertility  of  van't  Hoff's  teaching  of  osmotic- 
pressure  had  as  an  immediate  consequence  its  unrestricted 
application  to  all  manner  of  life  problems.  The  cells 
were  looked  upon  as  liquid  masses  surrounded  by  semi- 
permeable membranes  which  were  supposed  to  act  as 
Pfeffer's  well-known  model.  A  relative  increase  in  the 
osmotic  pressure  of  the  fluids  surrounding  the  cells  was 
supposed  to  bring  about  a  shrinkage,  while  an  increase 
in  the  osmotic  pressure  of  the  cell  contents  over  that  of 
the  surrounding  fluid  was  supposed  to  be  followed  by  a 
swelling  of  the  cell.  This  so  simple  and  consequently 
so  enticing  conception  of  the  role  of  osmotic  pressure  in  the 
organism  meets,  however,  when  further  considered,  with 


36  PHYSICAL   CHEMISTRY  IN   MEDICINE. 

difficulties;  nor  does  it  furnish  even  the  possibilities  of  a 
complete  understanding  of  many  important  phenomena. 
In  spite  of  this,  however,  numerous  fundamental  investi- 
gations, such  as  those  of  Hamburger  and  Koppe,  con- 
tinue to  retain  great  value,  representing  as  they  do  the 
first  experiments  undertaken  in  the  study  of  a  new  subject. 
The  principles  employed  in  these  investigations  approxi- 
mate actual  conditions  only  more  or  less  coarsely;  they 
fail,  however,  to  explain  details  because  conditions  for  their 
employment  in  the  organism  are  satisfied  only  in  part. 
This  fact  leads,  however,  to  the  recognition  of  new 
physico-chemical  peculiarities  of  living  matter,  as  illus- 
trated, for  example,  in  such  discoveries  as  the  biological 
significance  of  the  distribution  law. 

The  osmotic  relations  between  animal  cells  and  their 
surrounding  media  were  studied  for  the  most  part  on 
red  blood-corpuscles.  These  give  off  their  red  coloring- 
matter  in  dilute  salt  solutions  as  soon  as  the  concentration 
of  the  salt  drops  below  a  certain  value.  The  lowest  con- 
centration of  different  salt  solutions  which  just  prevent 
the  "laking"  of  blood  are  said  by  Hamburger  to  be 
isotonic  with  each  other  and  are  regarded  as  bringing 
about  the  same  degree  of  swelling  in  red  blood-corpuscles. 
Since  a  determination  of  the  osmotic  pressures  of  such 
isotonic  salt  solutions  by  physical  methods  (determina- 
tion of  the  freezing-point)  showed  them  to  be  about  the 
same,  the  "blood-corpuscle  method"  was  looked  upon 
as  a  universally  applicable  procedure  for  determining 
osmotic  pressures.  An  extension  of  this  method  to  a 
large  number  of  crystalloids  soon  showed,  however,  that 
physical  and  physiological  isotonicity  are  identical  in 
only  a  few  substances,  the  majority  showing  differences 


CELLS  /1ND    TISSUES.  37 

between  the  two  (Hedin,  Gryns).  A  part  of  these 
exceptions  could  be  explained  by  Hedin,  and  more 
especially  by  KOppe,  on  the  ground  that  the  crystalloids 
permeate  the  red  blood-corpuscles  more  or  less  perfectly. 
K.OPPE  has  taken  the  following  stand:  The  solution  of  a 
red  blood-corpuscle  is  analogous  to  the  bursting  of  a 
balloon  filled  with  gas  in  a  rarefied  atmosphere.  This 
bursting  will  occur  also  when  the  space  about  the  ballo  n 
is  filled  with  a  gas  that  can  pass  through  the  wall  of  the 
balloon,  for  it  cannot  under  these  circumstances  counter- 
act the  pressure  existing  within  the  balloon.  In  this 
way  is  explained  the  laking  of  blood  in  even  the  most 
concentrated  solutions  of  substances  which  are  able  to 
pass  into  the  red  blood-corpuscles,  such  as  urea. 

If  this  simple  conception,  deduced  from  the  analogy 
between  gas  pressure  and  osmotic  pressure,  is  strictly 
tenable,  then  the  addition  of  substances  which  lake 
red  blood-corpuscles  (such  as  urea)  to  salt  solutions 
having  a  concentration  in  which  the  haemoglobin  just 
manages  not  to  pass  out  of  the  corpuscles  should  be 
without  effect,  since  the  relative  osmotic  conditions 
within  and  without  the  cells  remain  unchanged.  This  is, 
however,  not  the  case  ;  such  solutions  also  become  colored 
red.  Whenever  urea  has  been  added  to  a  NaCl  solu- 
tion a  much  higher  concentration  of  the  latter  is  required 
to  keep  the  red  blood -corpuscles  of  the  horse  from  losing 
their  haemoglobin  than  when  pure  NaCl  is  used.  The 
differences  in  concentration  varied  in  a  series  of  experi- 
ments between  0.005  and  0.01  molecular  NaCl,  and  were, 
strange  to  say,  not  markedly  influenced  by  an  increase 
in  the  concentration  of  the-  urea  from  0.25  to  1. 00  molecular. 

Not    until    thorough    investigations    have  "been    made 


3&  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

into  the  equilibrium  between  substances  that  dissolve 
and  those  that  inhibit  the  solution  of  red  blood-corpuscles, 
and  the  reversibility  of  the  migration  of  color,  can  we 
know  in  how  far  haemolysis  through  crystalloids  represents 
a  single  process.  The  idea  that  the  exit  of  haemoglobin 
from  the  red  blood-corpuscles  does  not  represent  a  single 
change,  as  rendered  apparent  through  the  action  of  such 
various  agents  as  electricity,  cold,  various  poisons,  etc., 
has  found  valuable  support  in  the  investigations  of 
Stewart  on  the  permeability  of  red  blood -corpuscles 
to  various  salts  (determination  of  electrical  conductivity 
of  plasma).  Only  the  failure  to  recognize  this  fact  is 
responsible  for  the  extensive  use  that  has  been  made  of 
the  determination  of  the  osmotic  resistance  of  the  eryth- 
rocytes in  the  solution  of  questions  in  the  physiology 
and  pathology  of  the  blood,  for  which  this  method  was 
never  adapted.  We  do  not  understand  the  conditions 
under  which  the  physiological  destruction  of  the  red  blood- 
corpuscles,  with  a  splitting  off  of  their  coloring- matter, 
occurs,  and  neither  the  discovery  of  normal  nor  of  patho- 
logical values  for  their  osmotic  resistance  yields  any  data 
from  which  conclusions  regarding  their  behavior  under 
experimental  (for  example,  removal  of  the  spleen)  or 
pathological  conditions  (icterus,  hsemoglobinuria,  etc.) 
may  be  drawn.  In  fact,  the  beautiful  investigations  of 
Bordet,  Ehrlich,  Landsteiner,  etc.,  on  the  production 
of  hemolytic  substances  in  the  animal  body  point  to  a 
new  field  of  work  entirely  outside  of  the  teachings  of 
osmotic  pressure. 

There  is  no  objection  to  saying  that  several  solutions 
which  have,  the  same  osmotic  pressure  are  isotonic,  that 
is,  isosmotic  with  each  other;  but  to  speak  of  the  isoto- 


CELLS  .-t\'D   TISSUES.  39 

nicity  of  a  single  solution  is  impossible,  as  Koppe  has  well 
pointed  out  by  indicating  the  confusion  wrought  by  this 
expression.  The  osmotic  effect  of  a  solution  may  be 
expressed  in  terms  of  molecular  concentration  (mol.).  The 
molecular  weight  of  a  non-dissociable  substance  (such 
as  cane-sugar),  expressed  in  grams  and  dissolved  in 
enough  water  to  make  a  liter,  constitutes  the  unit  of 
molecular  concentration.  Such  a  solution  has  an  osmotic 
pressure  of  22.35  atmospheres  at  o°  C.  Isotonic  solutions 
arc  cquimolecular. 

The  fact  that  there  exists  a  difference  between  physical 
and  physiological  determinations  of  osmotic  pressure  is 
emphasized  all  too  little.  In  the  former  case  the  pressure 
is  measured  against  the  solvent,  in  the  second  case  the 
pressure  of  a  solution  against  cells  or  their  contents. 
Each  of  these  values,  differing  as  it  docs  more  or  less 
from  the  other,  may  have  its  own  biological  signifi- 
cance. 

A  study  of  the  changes  in  the  volume  of  cells  brought 
about  through  differences  in  osmotic  pressure  clearly 
shows  that  the  conditions  for  the  unlimited  tenability  of 
van't  Hoff's  laws  do  not  exist  in  the  living  organism. 
In  its  simplest  form  van't  Hoff's  theory  presupposes 
two  things:  impermeability  of  the  separating  membrane 
for  the  dissolved  substance,  and  complete  freedom  of 
movement  of  the  solvent  throughout  the  entire  medium 
contained  within  the  membrane.  If  these  two  conditions 
existed  in  the  case  of  cells,  then  two  series  of  facts  should 
be  found  to  be  true  experimentally: 

I.  A  cell  should  have  the  same  volume  in  isosmotic 
solutions  of  different  substances. 

II.  A  cell  should  show  an  amount  of  change  in  volume 


4<3  PHYSICAL   CUB  MIS  TRY  IN  MEDICINE. 

proportional  to  the  amount  of  change  in  the  osmotic 
pressure  within  or  without  the  cell. 

It  was  soon  learned  to  attribute  the  exceptions  to  the 
first  sentence  to  the  relative  permeability  of  the  cells  for 
certain  substances.  But  this  explanation  does  not  suffice 
for  a  large  and  important  number  of  cases  in  which  the 
substance  that  has  entered  a  cell  exists  here  in  a  greater 
concentration  than  in  the  solution  surrounding  it.  These 
cases  have  been  explained  in  part  through  the  distribution 
law. 

Strange  to  say,  not  a  single  example  investigated  thus 
far  has  ever  brought  a  confirmation  of  the  second  con- 
clusion stated  above — a  change  in  volume  proportional 
to  the  change  in  osmotic  pressure.  Koppe,  for  example, 
found  that  it  was  the  rule  to  discover  very  considerable 
variations  from  this  law  in  the  red  blood-corpuscles. 
When  the  osmotic  pressure  of  the  surrounding  liquid  is 
increased,  the  decrease  in  the  volume  of  the  red  blood- 
corpuscles  is  less  than  calculated,  as  is  true  also  of  the 
amount  of  their  swelling  when  the  osmotic  pressure  in 
the  surrounding  fluid  is  decreased.  In  the  experiments 
carried  out  by  Durig  on  the  swelling  and  shrinkage  of 
frogs  great  exceptions  to  the  simple  laws  of  osmotic 
pressure  were  found  to  exist.  We  seem  to  have  every 
reason  for  believing  that  freedom  of  movement  and 
homogeneousness  of  solvent,  which  are  demanded  for  an 
immediate  application  of  van't  Hoff's  theory  to  the 
interchange  between  the  fluids  within  and  without  the 
cell,  do  not  exist  in  our  tissues.  A  chief  r61e  in  this 
modification  of  the  solvent  will  no  doubt  fall  to  the  part 
of    the    colloidal    constituents    of    living    matter.*     The 

*  It  does  not  seem  impossible  that  the  relations  found  to  exist  here 


CELLS  AND  TISSUES.  4* 

fad  thai  protoplasm  behaves  in  many  ways  as  a  mixture 
of  different  soL  ents  might  also  be  of  importance* 


V. 

A  peculiar  and  important  place  biologically  is  occupied 
by  those  crystalloids  which  because  of  their  behavior 
in  the  electric  current  (conductivity  and  electrolysis)  are 
called  electrolytes.  These  are  substances  which  in  aqueous 
solutions  (and  in  certain  other  solvents)  break  up  into 
electrically  charged  particles,  the  ions  (the  electronegative 
anion  and  the  electropositive  cation).  This  electrolytic 
dissociation,  which  may  in  dilute  solutions  attain  a  very 
high  grade,  is,  however,  never  complete;  beside  the  ions 
there  exist  also  non-dissociated,  electrically  neutral 
molecules.  The  investigation  of  the  role  of  electrolytes 
in  life  phenomena  must  be  directed  toward  an  under- 
standing of  the  part  played  by  each  of  these. 

Experiment  has  taught  us  that  there  exist  physiological 
effects  which  are  attributable  solely  to  ions.  The  vital 
property  of  the  ions  to  keep  in  solution  the  -widely 
di>tributed  globulins  cannot   be  replaced   by  any  other 

may  be  expressed  mathematically.  Support  for  this  is  found  in  the 
no  longer  negligible  volume  <>f  molecules  present  in  colloidal  mixtures 
which  bind  the  solvent.  The  water  found  in  gels  is,  moreover,  to  be 
regarded  as  freely  movable  only  in  part,  and  this  part  decreases  rapidly 
witli  an  increase  in  the  amount  of  shrinkage.  In  consequence  of  the 
increase  in  the  values  of  the  volume  and  the  attraction  cf  the  gas  mole- 
cules the  simple  equation   pv—R.T.  no  longer  holds,  as  is  well  known, 

at  higher  temperatures,  but  van  i>kr  Waal's  equation  (/>  +  —  )  (v  —  b)  = 

R.T.      Much    seems    to  speak  in   favor    of  the    idea    that    the   relation 

between  osmotic    pressure  ami  i  ell  volume  may  be  kindred  to  the  latest 

modification  of  the  law  of  Mario tte-Boyle. 


42  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

kind  of  dissolved  crystalloids  (Pauli).  The  poisonous 
effects  of  water  poor  in  ions  upon  the  human  organism 
(Koppe)  may  also  belong  under  this  heading.*  Differ- 
ences in  the  concentration  of  ions  brought  about  through 
differences  in  their  migration  velocities  constitute  the 
source  of  differences  in  electrical  potential.  Loeb  was 
probably  the  first  who  recognized  in  such  "concentration 
chains"  the  cause  of  the  majority  of  the  electrical  phe- 
nomena observed  in  animal  organs. 

We  are  far  from  a  satisfactory  insight  into  the  nature 
of  the  effects  of  ions  the  elements  of  which  may  be 
electrical  in  character.  Nevertheless,  we  know  enough 
to  be  able  to  say  definitely  that  a  certain  effect  is  quan- 
titatively determined  by  ions,  if  it  follows  the  general 
principles  outlined  below: 

"Since  very  dilute  solutions  of  electrolytes  are  almost 
completely  dissociated,  the  effects  brought  about  by  such 
solutions  may,  as  a  rule,  be  looked  upon  as  ion  effects, 
and  the  electrically  neutral  molecules  may  be  neglected 
because  of  their  exceedingly  small  number.  A  pure  ion 
effect  must  parallel  the  concentration  of  the  ions  and  not 
the  concentration  of  the  substance  itself;  and  at  the  same 
concentration  of  substance  be  dependent  upon  the  degree 
of  dissociation,  which  can  be  varied,  without  a  change  in 
volume,  through  the  addition  of  an  electrolyte  having  a 
common  or  a  different  ion.      When    anion    and    cation 


*  A  specific  ion  effect  is  not,  strictly  speaking,  proved  by  this  experi- 
ment, because  the  attempt  to  do  away  with  the  poisonous  effects  of  the 
water  through  the  addition  of  non-ionized  substances  such  as  sugar 
was  not  made.  Moreover,  Nansen  and  his  followers  in  his  polar  expe- 
dition drank  for  months  without  harm  the  almost  ion-free  water  ob- 
tained by  melting  natural  ice. 


CELLS  AND   TISSUES  43 

both  take  part  in  the  ion  effed  ii  must  be  possible  to 
demonstrate  the  law  of  additive  ion  effects.  If,  however, 
the  ion  effect  is  connected  with  but  one  of  the  ions, 
then  it  is  dependent  only  upon  the  concentration  of  the 
effective  ion,  and  a  variation  in  the  opposite  ion  must, 
under  otherwise  unchanged  conditions,  be  indifferent. 
The  role  of  the  electrically  neutral  molecules  springs 
into  prominence  in  proportion  as  the  degree  of  electro- 
lytic dissociation   is  decreased." 

Examples  of  such  ion  effects  are  to  be  found  in  the 
papers  of  Dreser  on  the  pharmacology  of  mercury,  of 
Loeb  on  the  absorption  of  water  by  muscle  and  in  his 
much-discussed  experiments  on  artificial  parthenogenesis, 
of  Hober  on  the  sense  of  taste,  of  Spiro  with  Scheurlen 
and  Bruns,  as  well  as  Paul  and  Kronig,  on  the  founda- 
tions of  disinfection,  of  Pauli  on  changes  in  state  in  the 
proteins,  etc.  The  laws  governing  the  simultaneous 
action  of  several  electrolytes  can  also  be  deduced  from 
the  ionic  theory.  Pauli  and  Rona  have  recently  dis- 
covered an  antagonism  between  the  effects  of  different 
electrolytes  and  some  non-electrolytes  on  the  changes  in 
state  in  colloids. 

In  the  living  animal  we  have  to  deal  with  complex- 
mixtures  of  crystalloids  and  colloids,  between  which 
there  exist  relations  so  varied  that  they  are  in  part  still 
incapable  of  investigation.  Connected  with  the  uninter- 
rupted vital  activity  of  the  cell,  the  anabolism  and  cat- 
abolism  of  its  substance,  is  the  conversion  of  crystalloids 
into  colloids  and  colloids  into  crystalloids,  and  this  at 
present  still  entirely  unexplained  transformation  serves 
at  one  time  to  protect  a  substance  from  oxidation,  as  in 
the  conversion  of  sugar  into  the  colloidal  glycogen,  while 


44  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

at  another  it  protects  the  protoplasm  against  the  poisons 
of  its  own  products.  Questions  in  absorption,  secretion, 
pharmacology,  and  immunity  are  connected  with  these 
changes  in  state,  a  discovery  of  the  nature  of  which 
must  constitute  one  of  the  great  aims  of  biochemical 
research. 

3.  The  Colloidal  State  and  the  Reactions  that  Go  On  in 
Living  Matter.* 


Colloidal  material  enters  into  the  construction  of 
living  matter  in  two  forms — first,  in  the  liquid  or  solid 
state,  in  Graham's  sense  of  the  word,  and,  second,  in 
the  form  of  a  more  or  less  solid,  swollen  mass,  at 
times  sufficiently  solid  to  have  independent  form,  at 
others,  because  of  its  approximation  to  the  semi-solid 
condition,  still  subject  to  the  laws  of  surface  tension 
governing  liquids.  We  wish  to  consider  in  this  paper 
some  of  the  properties  of  this  swollen  (jelly-like)  condition 
which  can  be  attained  not  only  through  the  absorption 
of  the  so-called  "solvent"  by  the  original  solid  material — 
for  example,  the  absorption  of  water  by  dry  gelatine — but 
also  through  "gelation"  of  the  liquid  colloid.  This 
gelatinous  state  is  of  the  greatest  interest  to  the  biologist 
in  that  it  represents  a  state  of  aggregation  in  which  the 
properties  of  a  solid  and  those  of  a  liquid  are  often  united, 
a  condition  which  is  so  frequently  necessary  in  living 
matter.     For  this  reason  the  experiments  that  have  been 

*  From  Naturwissenschaftliche  Rundschau,  1902,  XVII,  p.  312. 
Address  delivered  before  the  Morphologisch-physiologische  Gesellschaft 
in  Vienna,  May  13,  1902, 


THE  COLLOIDAL  STATE.  45 

undertaken  to  obtain  a  better  knowledge  of  the  inner 
structure  of  these  jellies,  partly  from  the  standpoint  of 
the  morphologist,  partly  from  thai  of  the  physical  chemist, 

h:ivt    not    remained   without    influence   upon    important 
problems  in  general  physiology. 
The  systematic  investigations  of  Butschli,  extending 

over  more  than  a  decade,  tended  to  show  that  a  fine 
honeycomb  structure  is  present  in  all  jellies,  that,  for 
example,  ordinary  solid  gelatine  when  it  has  "set"  con- 
sists of  a  framework  made  up  of  delicate  gelatine  walls, 
and  that  in  this  framework  is  contained  a  fluid  gelatine 
of  a  low  concentration.  Expressed  physico-chemically, 
every  such  jelly  represents,  therefore,  a  diphasic  system, 
for  we  call  every  physically  or  chemically  homogeneous 
constituent  of  a  heterogeneous  complexity  a  phase.  Other 
investigators  looked  upon  the  results  they  obtained  in 
expression  experiments  on  jellies  as  furnishing  further 
proof  for  the  existence  in  them  of  a  homogeneous  fluid 
phase  beside  a  solid  supporting  framework,  and  this  in 
spite  of  variations  in  the  amount  of  gelatine  contained  in 
the  expressed  liquid  and  its  dependence  upon  the  amount 
of  pressure  employed.  These  observations  have  led  to 
the  conclusion  that  living  matter,  too,  is  to  be  looked 
upon  as  made  up  of  a  honeycomb  structure  just  as  other 
colloids — a  view  which  has  been  more  and  more  adopted 
by  physiologists  and  which  has  been  utilized  to  render 
intelligible  mechanical  and  chemical  changes  which  go  on 
in  living  matter.  Butschli  has,  for  example,  used  the 
radiating  figures  which  appear  about  gas-bubbles  in 
gelatine  to  explain  the  astrospheres  which  appear  during 
cell  division,  for  an  undisputed  similarity  exists  between 
the    two    pictures.    Questions    in    absorption    and    the 


46  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

spacial  differentiation  of  chemical  processes  have  also 
seemed  capable  of  a  seductively  simple  solution  by  belief 
in  the  existence  of  a  finely  chambered  structure  in  living 
matter. 

Against  the  very  considerable  evidence  that  has  been 
brought  forward  for  the  existence  of  the  honeycomb 
structure,  any  other  conception  of  the  constitution  of 
jellies  could  hope  to  receive  but  little  attention.  Never- 
theless, the  attempt  is  once  more  to  be  made  in  the 
following  pages  to  enter  into  a  discussion  of  this  difficult, 
but  for  the  biological  chemist  so  important,  question  of 
the  structure  of  jellies.  This  will  be  followed  by  a  dis- 
cussion of  the  possibility  of  explaining  certain  funda- 
mental properties  of  living  matter  which  have  been 
looked  upon  as  an  expression  of  its  honeycomb  structure 
independently  of  such  a  structure. 

II. 

Jellies  are  capable  of  a  separation  into  two  sharply 
defined  phases ;  in  other  words,  they  can  be  precipitated 
or  coagulated.  Such  a  precipitation  can  be  brought 
about,  for  example,  through  the  addition  of  the  sulphates, 
acetates,  tartrates,  or  citrates  of  the  alkali  metals.  For 
the  sake  of  clearness  we  will  base  our  considerations  upon 
the  behavior  of  gelatine,  which  represents  one  of  the 
most  thoroughly  studied  among  the  jellies.  The  separa- 
tion during  precipitation  of  a  phase  rich  in  gelatine 
from  one  that  is  poor  can  be  observed  not  only  micro- 
scopically, but  also  by  allowing  the  precipitate  to  settle 
to  the  bottom  of  the  vessel  while  kept  in  a  thermostat, 
when  the  phase  poor  in  gelatine  forms  a  distinct  layer 


THE   COLLOIDAL  STATE.  47 

over  that  rich  in  gelatine.  It  will  be  well  to  compare  first 
of  all  the  laws  governing  this  change  in  state,  which  is 
so  well  characterized  through  the  formation  of  two  phase  , 
with  the  laws  governing  the  solidification  or  gelation  of 

colloids,  for  which,  as  has  already  been  discussed,  a  sep- 
aration into  two  phases  is  also  looked  upon  as  a  distin- 
guishing characteristic. 

Investigations  which  have  been  carried  on  during 
past  years  have,  however,  disclosed  a  whole  series  of 
marked  differences  between  these  two  processes,  the 
more  important  of  which  are  now  to  be  briefly  touched 
upon. 

The  gelation  velocity  and  the  gelation-point  of  gelatine 
are  always  more  or  less  influenced  through  the  addition 
of  crystalloids,  which  at  times  hasten,  at  other  times  inhibit 
gelation,  when  compared  with  the  gelation  when  pure  water 
only  is  used.  This  influence  of  the  crystalloids  is  a  pro- 
gressive one  and  increases  in  proportion  to  the  amount 
added. 

The  precipitation  of  gelatine  is,  on  the  other  hand, 
strictly  connected  with  the  addition  of  definite  amounts 
of  the  precipitating  agent,  amounts  less  than  are  sufficient 
for  actual  precipitation  being  without  effect. 

While  all  crystalloids  modify  the  process  of  gelation, 
even  though  they  do  this  in  different  degrees  and  in 
different  directions,  only  certain  crystalloids  are  precipi- 
tating agents,  while  the  others  do  not  possess  this  power 
even  in  the  most  concentrated  solutions.  Gelatine,  for 
example,  is  precipitated  only  through  certain  electrolytes, 
non  ionized  crystalloids  being  effective  at  no  concentra- 
tion. Xon-conductors,  such  as  urea  and  dextrose,  can, 
however,  influence  the  process  of  gelation  just  as  effectively 


48  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

as  electrolytes,  and  this  in  both  directions.  Urea  inhibits 
gelation,  while  dextrose  favors  it. 

If  gelation  consisted  fundamentally  in  the  formation 
of  a  phase  rich  in  gelatine,  then  one  would  expect  to 
find  all  precipitating  salts  among  those  substances  which 
favor  gelation.  This  is  true,  however,  of  only  a  part  of 
the  precipitating  agents;  the  precipitating  chlorides  of 
potassium  and  sodium  exert  even  a  liquefying  action  upon 
gelatine  to  a  considerable  extent. 

The  following  fact  also  speaks  in  favor  of  a  strict 
separation  between  the  two  kinds  of  changes  in  the  col- 
loidal state. 

If  the  gelation-points  are  plotted  as  ordinates,  the 
molecular  concentrations  of  the  added  crystalloids  as 
abscissas,  one  obtains  curves  which  readily  indicate  the 
dependence  of  the  gelation  upon  the  added  crystalloid. 
These  curves  show  no  irregularities  throughout  their 
course,  not  even  when  the  amounts  added  approximate 
very  closely  those  at  which  precipitation  occurs. 

When  several  substances  are  allowed  to  act  together,  the 
differences  between  the  laws  governing  precipitation  and 
those  governing  gelation  also  evidence  themselves.  It  could 
be  shown  on  a  large  series  of  crystalloids  that  when  more 
than  one  are  allowed  to  act  simultaneously  upon  a  colloid 
the  effects  of  the  separate  crystalloids  upon  gelation  add 
themselves  algebraically.  This  summation  of  the  effects 
of  the  individual  crystalloids  is  not  altered  when  electro- 
lytes are  combined  with  non-electrolytes,  or  these  with 
each  other,  nor  by  the  fact  that  through  the  combination 
of  electrolytes  having  a  common  ion  the  degree  of  dis- 
sociation is  reduced,  nor  by  the  valency  of  the  ions. 

But  matters  are  entirely  different  when  the  gelatine 


THE   COLLOIDAL   STATE.  49 

is  precipitated.  The  meeting  of  two  electrolytes  with  a 
common  ion  favors  precipitation,  while  i  ertain  mm- 
electrolytes,  such  as  urea  and  sugar,  inhibit  through 
their  presence  the  precipitating  power  of  electrolytes,  and 

even  cause  already  existing  precipitates  to  go  back  into 
solution.  These  differences  between*  the  two  changes 
in  state  may  be  made  still  clearer  by  citing  a  few 
examples.  Thus  gelation  is  greatly  inhibited  through 
the  presence  of  bromides,  while  precipitation  through 
electrolytes  is  markedly  increased  as  soon  as  the  added 
bromide  contains  a  common  ion.  The  combination 
sodium  acetate — sodium  bromide  with  the  common  Na 
ion  is  in  this  way  a  more  powerful  precipitating  agent 
than  the  acetate  itself.  Again,  dextrose  favors  gelation 
in  that  it  elevates  the  gelation-point  and  increases  the 
gelation  velocity,  and  yet  it  inhibits  the  formation  of  a 
precipitate  through  a  precipitating  electrolyte  as  soon  as 
the  sugar  is  present  in  sufficient  amount. 

The  independence  oj  the  two  changes  in  state  evidences 
itselj  in  ill  is  also,  that  through  suitable  selection  oj  experi- 
mental conditions  it  is  possible  to  produce  precipitates 
in  a  solid  and  clear  gelatine  just  as  in  a  liquid  one,  and 
this  without  a  change  in  the  state  oj  aggregation  oj  the 
solid  gelatine. 

It  seems  to  me  that  what  has  been  said  proves  without 
question  that  between  the  precipitation  and  the  gelation 
of  a  colloid,  at  the  basis  of  which  fundamentally  similar 
changes  have  been  supposed  to  lie,  there  exist  in  reality 
profound  differences  through  which  the  assumption  of  a 
related  origin  of  the  two  phenomena  has  been  rendered 
most  improbable.  In  the  same  direction  will  be  found 
to  point  an  analysis  of  those  facts  which  have  always 


5o  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

been  considered  as  sufficient  evidence  for  the  primary 
coagulation  structure  of  all  solid  colloids. 


III. 

The  beginning  of  those  investigations  of  Butschli  on 
colloidal  structures  which  must  be  considered  in  the  gen- 
eral question  that  lies  before  us  were  observations  on 
microscopic  foams  of  gelatine  and  olive-oil,  which  when 
properly  prepared  furnish  a  framework  of  solidified  gela- 
tine walls  in  the  chambers  of  which  is  inclosed  the  fluid 
oil. 

Butschli  found  that  the  structures  which  can  be 
obtained  through  typical  coagulation  of  colloids  are  also 
built  according  to  this  plan.  Thin  layers  of  egg  albumin 
coagulated  through  heat  or  those  precipitating  agents 
which  are  generally  known  as  "fixing-agents, "  or  aca- 
cia solutions  precipitated  with  alcohol,  precipitated 
liquid  (peptonized)  gelatines,  etc.,  all  show  under  the 
microscope  the  same  characteristic,  finely  honeycomb 
structure.  Up  to  this  point  the  conclusions  of  the  Heidel- 
berg zoologist,  which  are  of  great  interest  to  the  molecular 
physicist  also,  show  a  complete  harmony  between  obser- 
vation and  interpretation;  and  the  value  of  Butschli's 
discoveries  for  the  morphologist  who  utilizes  analogous 
methods  to  render  apparent  cell  structures  is  not  to  be 
underestimated. 

In  the  further  course  of  his  observations  on  colloids 
Butschli  later  concludes,  from  a  study  of  substances  in 
the  condition  of  swelling  (jellies),  that  these  also  have  a 
true  honeycomb  structure  identical  with  that  observed 
in  coagulation  foams  and  in  typical  coagulations.     Only 


THE  COLLOIDAL   STATE.  51 

this  honeycomb  structure  is  ordinarily  not  convincingly 
demonstrable;    it    becomes    distinctly   visible,    however, 

under  certain  experimental  conditions. 

A  closer  study  of  the  conditions  which  make  apparent 
the  honeycomb  structure  teaches  us,  however,  that  we 
have  to  deal  in  every  case  with  the  introduction  of  true 
coagulation  or  precipitation  phenomena  governed  by  the 
laws  already  outlined  above.  By  far  the  most  thorough 
investigations  bearing  upon  this  subject  have  also  been 
carried  out  on  solidified  gelatine,  and  upon  these  Butschli 
supports  in  the  main  his  belief  in  the  primary  honey- 
comb structure  of  all  swollen  media,  and  consequently 
also  that  of  native  protoplasm. 

But,  as  has  already  been  pointed  out,  even  though 
neither  direct  observation  nor  tinctorial  methods — and 
this  in  spite  of  the  well-known  marked  affinity  of  gelatine 
for  dyes — have  rendered  it  possible  to  prove  the  existence 
of  a  honeycomb  structure  in  untreated  gelatines,  such  a 
structure  is,  nevertheless,  supposed  to  exist  in  all  prob- 
ability. The  reasons  which  Butschli  has  brought  for- 
ward in  support  of  this  idea  can  only  very  briefly  be  given 
here  and  their  tenability  be  tested. 

The  reason  why  it  is  normally  impossible  to  see  the 
walls  constituting  the  framework  of  gelatine  is,  according 
to  one  author,  dependent  in  part  upon  the  fact  that  they 
are  1  (liable  and  when  dried  in  vacuo,  for  example,, adhere 
closely  to  each  other,  in  part  upon  the  fact  that  the 
difference  between  the  indices  of  refraction  of  the  walls 
of  the  framework  and  of  the  substance  found  within 
them  is  too  little  to  give  distinct  pictures.  These  walls 
of  the  honeycomb  structure  can,  however,  be  rendered 
more  solid  and  dense  through  the  action  upon  them  of 


5  2  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

chromic  acid,  alcohol,  or  ether,  when  their  optical  recog- 
nition is  made  much  easier.  Any  one  can  at  any  time 
prove  to  himself  that  a  thin  layer  of  gelatine  when  treated 
with  dilute  chromic  acid  according  to  Butschli' s  instruc- 
tions becomes  opaque  and  white,  and  shows  under  the 
microscope  a  very  regular,  finely  chambered  structure . 
entirely  identical  with  the  picture  found  in  true  coagula- 
tions of  colloids.  But  we  are  supposed  to  deal  here  not 
with  a  true  coagulation,  but,  as  Butschli  expresses  it 
in  a  by  no  means  clear  and  unequivocal  way,  with  a 
"kind  of  coagulation"  through  which  a  preformed  struc- 
ture becomes  visible. 

That  structures  which  have  been  produced  through  the 
action  of  alcohol  disappear  when  put  into  water,  to 
reappear  in  exactly  the  same  form  when  subjected  a 
second  time  to  the  action  of  alcohol,  does  not  argue  at 
all  in  favor  of  the  primary  nature  of  the  structure.  The 
explanation  of  this  phenomenon  is  easily  .found  in  the 
well-known  properties  of  the  changes  in  state  which 
colloids  suffer.  The  change  which  is  brought  about  in 
gelatine  through  alcohol  is,  in  contrast  to  that  produced 
through  chromic  acid  for  example,  simply  reversible. 
Since,  however,  changes  in  state  take  place  only  very 
slowly  in  gels,  these  are,  if  at  all,  only  gradually  and 
scarcely  completely  reversible.  It  is  readily  intelligible, 
therefore,  why  under  these  circumstances  structures 
which  have  once  been  produced  and  which  are  not 
entirely  destroyed  even  through  remelting  of  the  gelatine 
reappear  in  their  old  form. 

That  a  fluid  condition  of  the  colloid  is  necessary  for 
the  production  of  coagulation  structures,  as  Butschli 
believes,    and    that    these    structures    must    be    present 


THE  COLLOIDAL  STATE.  53 

as  soon  as  the  colloid  solidifies,  can  be  readily  shown  to 
be  untrue  through  the  production  of  precipitates  in  clear, 
solidified  gelatine.  For,  since  the  precipitation  limit>  of 
many  electrolytes,  such  as  the  sulphates,  citrates,  and 
tartrates  of  the  alkali  metals,  arc  dependent  upon  tem- 
perature in  such  a  way  that  they  are  lowered  with  a  de- 
crease in  the  temperature,  it  is  an  easy  matter  to  prepare 
salt-gelatines  in  which  heavy  precipitates  do  not  appeal 
until  the  solidification  temperature  has  been  long  passed 
— in  other  words,  in  the  clear  and  solid  gelatine.  Such 
coagulations  are  subject  to  the  well-defined  effects  of 
coagulation  "germs"  in  the  same  way  as  those  which 
occur  in  a  fluid  medium.  The  beautiful  figures  which 
Liesegang  has  been  able  to  produce  in  colloids  with 
the  aid  of  precipitates  all  rest,  in  the  main,  upon  the 
"germ"  action  of  previously  produced  coagulations.  In 
such  processes  is  also  found  an  unforced  explanation  of 
the  phenomenon,  used  by  Butschli  as  an  argument  in 
favor  of  the  existence  of  a  primary  honeycomb  structure, 
that  delicate  granules  when  suspended  in  gelatine  arc 
always  found  in  the  nodal  points  and  walls  of  the  frame- 
work. The  reason  for  this  is  that  these  foreign  bodies 
all  act  as  coagulation  germs.  For  the  same  reason,  the 
chambers  of  the  honeycomb  structure  arrange  themselves 
in  rows  which  correspond  with  the  lines  produced  on 
the  slide  in  polishing  it.  And  just  as  little  will  we  be  able 
to  consider  it  proof  of  a  preformed  foam  structure  that 
the  coagulations  which  take  place  in  colloids  mirror  all 
the  stresses  that  appear  in  it,  due  in  part  to  shrinkage 
while  drying,  in  part  to  the  contraction  of  cooling  air 
bubbles. 
As  further  support  for  belief  in  a  preformed  structure, 


54  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

observations  are  utilized  which  are  noticed  when  delicate 
gelatine  threads  that  have  been  kept  in  absolute  alcohol 
or  have  been  dried  in  the  air  are  subjected  to  the  effects 
of  tension  or  pressure.  If  such  threads  are  stretched  or 
bent,  microscopic  examination  reveals  a  cross-striation 
upon  their  surface  corresponding  with  parts  of  the 
threads  that  have  become  white  and  opaque.  The  cen- 
tral portion  of  the  threads  may  retain  its  hyaline  char- 
acter. That  we  are  dealing  in  this  case  with  more  or 
less  well-marked  breaks  in  continuity  is  without  question 
when  the  manner  of  their  production  is  considered. 
Butschli  explains  the  regularity  of  the  pictures  which 
are  produced  by  saying  that  the  chambers  of  the  stretched 
honeycomb  structure  of  the  gelatine  give  rise  to  a  system 
of  stripes  which  cross  each  other  diagonally,  just  as  is 
the  case  with  a  net  when  this  is  pulled  in  certain  direc- 
tions. It  would  be  an  argument  in  favor  of  this  explana- 
tion if  it  could  be  shown  that  in  gelatine  threads  which 
had  previously  not  been  treated  with  fixing-agents  the 
distance  between  the  stripes  is  less  than  the  diameter  of 
one  of  the  honeycomb  chambers.  This  is,  however,  not 
the  case.  In  a  large  number  of  measurements  Butschli 
has  determined  the  diameter  of  the  latter  to  be  0.7  /*  in 
gelatine  that  has  been  treated  with  chromic  acid  or 
alcohol,  while  the  distance  between  the  stripes  in  untreated 
gelatine  threads  is  2.1  to  2.3  \x.  That  the  honeycomb 
structure  of  gelatine  threads  which  have  been  treated 
with  precipitating  agents  is  more  or  less  cross-striated 
cannot  seem  strange  when  the  systems  of  cross-striation 
are  looked  upon  as  expressions  of  a  definite  distribution 
of  tension  and  pressure  in  the  threads.  As  has  already 
been  described  above,  such  stresses  may  impress  them- 


THE   COLLOIDAL   ST  A  TIL  55 

Selves  upon  coagulations  also,  and  under  favorable  con- 
ditions may  evidence  themseh  es  even  about  fine  suspended 
granules.  A  satisfactory  explanation  of  the  fact  that  ten- 
sion alone  may  make  a  honeycomb-like  structure  visible, 
Butschli  is  unable  to  give,  because  of  lack  of  observa- 
tions directed  toward  this  point.  Hut  surface  structures 
similar  to  those  described  above  frequently  appear  in 
different  substances  that  have  been  stretched  or  com- 
pressed, in  part  as  an  expression  of  the  incomplete 
mechanical  homogencousness  of  these  bodies.  Honey- 
comb and  fibrillar  pictures  are  found  on  the  surface  of 
stretched  and  compressed  metals,  and  we  can  justly 
put  into  this  class  also  the  cross-striated  structures  ob- 
served by  Butschli  on  delicate  threads  of  Canada  balsam, 
without  assuming,  with  this  author,  that  this  resin  also 
possesses  a  preformed  honeycomb  structure.  Interesting 
and  worthy  of  further  study  as  these  observations  may 
be,  they  furnish  conclusive  evidence  of  the  primary 
honeycomb  structure  of  colloids  just  as  little  as  the 
already  described  experiments  dealing  with  the  question 
of  rendering  this  structure  visible.  That  we  are  dealing 
with  a  true  coagulation  whenever  a  structure  is  rendered 
visible,  and  not,  as  Butschli  thinks,  with  a  condensation 
of  primary  supporting  walls,  in  a  certain  sense  a  more 
advanced  stage  of  simple  gelation,  is  shown  by  the  follow- 
ing experiment,  which  to  my  mind  is  conclusive. 

In  order  to  recognize  its  nature,  let  us  recall  to  mind 
the  already  discussed  laws  governing  coagulation,  on  the 
one  hand,  and  gelation,  on  the  other,  under  the  influence 
of  combinations  of  electrolytes  and  non-electrolytes. 
These  two  classes  of  substances  add  themselves  alge- 
braically in  their  effect  upon  gelation,  while  the  coagu- 


$6  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

lation  brought  about  through  electrolytes  does  not  occur 
if  such  non- electrolytes  as  urea  or  sugar  are  present;  in 
fact,  an  already  existing  coagulum  is  made  to  go  back 
into  solution  when  these  substances  are  subsequently 
added.  If  thin  layers  of  gelatine  spread  upon  slides  are 
introduced  for  fifteen  minutes  into  a  0.3  per  cent,  chromic 
acid  solution  kept  at  an  even  temperature  of  about  230  C, 
the  beautiful  coagulation  structures  are  produced  which 
Butschli  has  described  and  pictured.  As  soon,  how- 
ever, as  urea  is  added  to  the  chromic  acid  solution  in  the 
concentration  of  1.0  molecular,  the  gelatine  does  not 
become  opaque,  and  a  formation  of  structure  as  described 
above  does  not  take  place,  even  when  everything  else  in 
the  experiment  is  arranged  as  before.  The  gelatine 
remains  clear,  and  examination  with  even  the  highest 
powers  of  the  microscope  shows  it  to  be  homogeneous. 
Urea  in  the  concentration  of  0.25  molecular  is  without 
effect,  while  concentrations  above  2.0  molecular  lead  to 
excessive  swelling  and  solution  of  the  layer  of  colloidal 
material.  That  we  are  dealing  in  this  experiment  not 
with  the  inhibiting  effects  of  urea  upon  gelation,  but 
with  its  anti-coagulating  effects,  is  shown  by  the  follow- 
ing. Chlorides  cause  an  excessive  swelling  and  prevent 
gelation  in  the  same  way  as  urea,  a  2.0  molecular  sodium 
chloride  solution  being  equal  to  a  1.0  molecular  urea 
solution.  Yet  chlorides  have  as  electrolytes  no  inhibiting 
effect  upon  coagulation.  Corresponding  with  these  facts, 
it  is  found  that  an  addition  of  sodium  chloride  to  the 
chromic  acid  solution  equivalent  in  effect  to  an  adequate 
amount  of  urea  does  not  at  all  prevent  the  formation  of 
the  typical  coagulation  structures  in  the  gelatine  prep- 
arations.    These  experiments  prove  definitely  that  in  the 


THE   COLLOIDAL  STATE.  57 

formation  of  structures  in  gels  we  arc  dealing  with  true 
coagulations.  The  experiments  may  easily  be  varied  and 
similar  results  be  obtained  by  using  other  fixing  agents  and 
non-electrolytes.  It  may  be  pointed  out,  in  passing,  that 
histology  could  easily  employ  to  advantage  this  property 
of  the  non-electrolytes,  especially  that  of  urea,  for  obtain- 
ing a  finer  gradation  in  its  methods  of  hardening  and 
fixing  tissues,  as  well  as  for  causing  changes  brought 
about  through  these  methods  to  disappear  more  or  less 
perfectly. 

All  physico-chemical  investigations  that  have  been  de- 
scribed here  indicate,  therefore,  that  the  condition  0} 
swelling  in  colloids  is  not  to  be  looked  upon  as  a  diphasic 
one,  and  that  the  reasons  which  have  thus  far  been 
advanced  in  favor  of  such  an  assumption  do  not  bear 
careful  criticism.  We  can  therefore  find  in  the  prop- 
erties of  the  jellies  no  arguments  for  believing  that  proto- 
plasm is  a  strictly  diphasic  system  having  a  finely 
honeycomb  structure.  No  doubt  the  substance  of  the 
cell  may,  in  those  instances  in  which  we  have  to  deal 
with  inclusions  of  such  substances  as  colloidal  carbo- 
hydrates or  fats,  represent  a  heterogeneous  complexity 
with  phases  the  relations  of  which  to  each  other  arc 
subject  to  the  laws  of  chemical  equilibrium.  In  general, 
however,  such  inclusions  take  part  only  indirectly  in  the 
actual  life  processes  of  the  cell.  At  present  no  cogent 
reason  exists  for  not  believing  that  the  mass  which  is 
looked  upon  as  the  bearer  of  life  processes  may  not  well 
be  monophasic  in  structure. 

According  to  a  view  expressed  years  ago  and  based  on 
studies  of  the  way  in  which  water  is  held  in  gel-,  the 
colloidal   particles  of  the  latter  are   believed   to   contain 


5^  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

the  liquid  producing  the  swelling  in  combinations  vary- 
ing from  those  that  are  exceedingly  loose  to  those  that 
are  very  firm.  In  this  way  is  rendered  possible  a  great 
diversity  in  absorption  phenomena  as  well  as  the  formation 
of  solid  and  liquid  solutions.  From  this  metastabile  con- 
dition of  equilibrium  the  gel  gradually  endeavors  to 
attain  one  in  which  all  the  colloidal  particles  are  swollen 
to  the  same  degree.  In  living  matter  colloidal  material 
is  being  constantly  broken  down  and  built  up  anew,  and 
in  this  way  the  progress  toward  a  final  condition  of 
equilibrium  in  the  molecular  disposition  of  the  liquid 
producing  the  swelling  is  steadily  destroyed. 

IV. 

The  colloidal  constitution  of  living  matter  is  intimately 
connected  with  one  of  the  most  important  problems  in 
biological  chemistry,  i.e.,  with  the  question  of  the  spacial 
differentiation  of  the  chemical  reactions  in  protoplasm. 
Since  colloids  resist  the  diffusion  into  them  of  other  col- 
loids, it  is  self-evident  that  through  the  presence  of 
different  colloids  within  a  cell  as  many  different  localities 
are  provided  in  which  chemical  reactions  having  a  more 
or  less  different  course  may  take  place.*  With  the 
exception  of  these  coarser  divisions  between  chemical 
reactions,  physiological  experience  compels  us  to  believe 
that  chemical  reactions  of  the  most  different  kinds  are 
simultaneously  possible  in  the  homogeneous,  colloidal 
ground-substance  of  the  cell.     In  even  the  smallest  par- 

*  The  great  importance  of  the  differentiation  of  the  cell  into  nucleus 
and  cell  body  has  been  proven  beyond  question.  Reactions  that  are 
connected  with  the  heterogeneous  constitution  of  the  cell  no  longer 
take  place  when  the  cell  is  destroyed  mechanically. 


THE  COLLOIDAL   STATE.  59 

tick's  of  protoplasm  antagonistic  chemical  reactions,  such 
as  oxidation  and  reduction,  hydration  and  loss  of  water, 
condensation,  polymerization,  synthesis,  and  their  oppo- 
site, or,  generally  speaking  as  Hering  puts  it,  assimila- 
tion and  dissimilation,  are  able  to  occur  through  and 
beside  each  other. 

In  a  suggestive  lecture  on  the  chemical  organization 
of  the  cell,  one  of  the  greatest  of  present-day  biochemical 
investigators  has  thrown  much  light  on  this  important 
problem  and  has  assumed  for  its  solution  the  existence 
of  a  finely  chambered  structure  in  colloids  and  the  im- 
permeability of  the  colloidal  walls.*  Just  as  the  chemist 
allows  different  chemical  reactions  to  take  place  in  different 
vessels,  the  cell  is  believed  to  utilize  the  different  chambers 
of  its  honeycomb  structure  and,  with  the  help  of  the 
colloidal  ferments,  the  number  and  knowledge  of  which 
is  daily  growing,  allow  the  necessary  reactions  to  go  on 
independently  of  each  other. 

As  the  considerations  outlined  above  have  shown  that 
we  lack  at  present  any  adequate  foundation  for  believing 
that  living  matter  has  a  honeycomb  structure,  the  ques- 
tion arises  whether  it  is  possible  for  antagonistic  chemical 
reactions  to  take  place  in  exceedingly  small  spaces  with- 
out the  help  of  any  structure.  An  analysis  of  such 
antagonistic  reactions  brings  with  it,  I  believe,  their 
satisfactory  explanation,  based  upon  numerous  facts  and 
teachings  of  physical  chemistry. 

*  Hofmeister  (Naturw.  Rundschau,  1901,  XVI,  p. 581)  supports  the 

hypothesis  of  a  finely  chambered  structure  in  protoplasm  upon  chemical 

which    need   not  be  discussed  lure.     We  have  first  to  settle 

the  question  whether  antagonistic  reactions  can  at  all  take  place  in  a 

homogeneous  substrate 


60  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

The  chemical  reaction 

CH3COOH  +  QzHsOH^CHgCOOCaHs +H20 


Acetic  acid  Ethyl  alcohol  Ethyl  acetate  Water 

furnishes  a  picture  of  a  simple  reaction  which  may  take 
place  in  either  direction.  If  we  begin  with  a  mixture  of 
chemically  equivalent  amounts  of  acetic  acid  and  ethyl 
alcohol,  the  reaction  takes  place  from  left  to  right,  with 
the  formation  of  ethyl  acetate  and  water;  and  conversely, 
if  the  latter  are  added  to  each  other,  the  reaction  takes 
place  in  the  reverse  direction.  Whatever  the  starting- 
point,  the  final  result  is  a  definite  state  of  equilibrium 
between  all  the  end  products.  Depending  upon  the 
direction  toward  which  the  equilibrium-point  is  pushed, 
at  one  time  the  one  reaction,  at  another  time  the  other, 
may  have  the  upper  hand.  The  manner  in  which  such 
an  equilibrium-point  can  be  displaced  is  illustrated  by 
the  change  that  systems  such  as  the  above  suffer  under 
the  influence  of  an  increase  in  temperature.  According 
to  a  well-known  law,  an  increase  in  temperature  pushes 
the  equilibrium  toward  the  side  of  the  endothermic  reac- 
tion. 

The  following  equations,  in  which  letters  have  been 
used  in  place  of  different  chemical  formulas,  illustrate 
some  types  of  such  reactions  which  in  practice  take 
place  only  in  the  one  or  in  the  opposite  direction: 

A+m  =  B 
B-m=A  y 


THl-    COLLOIDAL  STATE.  61 

One  tan  at  any  time  imagine  cither  O  or  H2O  written 
into  (.iiuation  I  instead  of  in,  and  so  obtain  the  picture 
of  a  simple  reversible  reaction — an  oxidation  and  a  reduc- 
tion, or  a  hydration  and  a  loss  of  water,  following  the 
type  of  a  simple  reaction  which  may  take  place  in  either 
direction;  or  in  equation  II  a  condensation  or  a  hydro- 
lytic  cleavage.  General  biochemistry  has  until  now 
taken  notice  of  only  this  type  of  antagonistic  reaction, 
that  is  to  say,  reactions  which  counteract  each  other  in 
the  sense  of  positive  and  negative  values. 

There  exists,  however,  among  the  reaction  chains  in 
the  body  a  second  apparently  very  common  type  of 
antagonistic  reaction,  the  nature  of  which  can  be  best 
illustrated  by  certain  changes  in  physical  state  that 
colloids  are  capable  of  suffering. 

It  is  a  well-known  fact  that  with  the  customary  methods 
of  investigation  it  is  found  that  the  melting-point  and 
the  solidification- point  of  the  crystalloids  coincide.  It 
is  different,  however,  in  the  case  of  the  colloids,  in  which 
these  two  points  may  lie  some  distance  apart,  even  when 
the  changes  in  temperature  are  brought  about  most  care- 
fully. In  consequence  of  the  indolence  with  which 
changes  take  place  in  colloids,  superheating  and  under- 
cooling are  the  rule.  A  gelatine  the  temperature  of 
which  lies  between  the  melting-point  and  the  gelation- 
point  shows  in  consequence  a  peculiar  behavior.  If  such 
a  gelatine  is  cooled  to  beyond  the  gelation-point  and  is 
then  carefully  warmed  back  to  the  original  temperature, 
the  gelatine  remains  solid;  if,  however,  the  gelatine  is 
heated  to  beyond  the  melting-point  and  is  then  carefully 
cooled  down  to  the  starting  temperature,  it  remains 
liquid.     A  change  in  slate,  therefore,  impresses  itself  upon 


02  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

the  colloid  and  determines  the  condition  in  which  the 
colloid  will  ultimately  be  found.  In  other  words,  a  colloid 
seems  to  remember  more  or  less  perfectly  a  change  that 
it  has  suffered,  just  as  does  living  matter.  If  gelation 
and  melting  followed  the  same  course,  only  in  opposite 
directions,  then  a  gelatine,  when  it  has  returned  to  its 
original  temperature,  should  also  be  existing  in  its  original 
state,  no  matter  in  which  direction  it  had  previously 
suffered  a  change  in  temperature.  That  we  have  to  do 
in  this  case  with  reversible  changes  that  follow  different 
paths  is  evidenced  by  another  property  of  this  change 
in  state.  If  one  compares  the  curves  indicating  the 
melting-  and  gelation-points  of  gelatines  of  different 
concentrations,  obtained  by  plotting  the  concentrations 
upon  the  abscissas  and  the  corresponding  melting-  and 
gelation- points  upon  the  ordinates,  it  is  seen  that  the 
two  processes  are  dependent  in  different  ways  upon  the 
concentration  of  the  gelatine.  The  gelation  curves  follow 
an  approximately  straight  line;  the  melting  curves,  on 
the  other  hand,  rise  gradually,  but  in  a  decreasing  degree, 
above  the  abscissa. 

In  contrast  to  the  previously  described  simple  or  homo- 
drome  antagonistic  reactions,  which  follow  the  same 
course  in  either  direction  and  which  behave  at  any  stage 
as  mathematical  values  having  different  signs,  we  are 
dealing  in  this  case  with  complex  or  heterodrome  antag- 
onistic reactions,  which  reach  their  respective  end  states 
along  different  paths.     (See  Figs,  i  and  2.) 

In  what  follows  we  will  make  use  of  these  simple  dia- 
grams in  characterizing  the  antagonistic  reactions. 

Heterodrome  reactions  of  a  chemical  nature  play 
an  important  role  in  the  changes  that  go  on  in  living 


THE   COLLOID. II.   STATE.  63 

matter.      They   may    be   readily    illustrated    by    a   few 
examples. 

The  equations 

A+m =B  )  T 

a+b+c+  . . .  =A  )  Ua 

A  =l  +  m  +  n+  .  .  .  ) 

represent,   when  m  and   m'   indicate   differently  placed 
O  or  H:0   groups,  cases  in  which,  as   in  la,  oxidation 

<- 


Fig.  1. 

and  reduction,  or  hydration  and  splitting  off  of  water, 
follow  a  heterodrome  course;  or,  as  in  Ila,  cases  in  which 
the  decomposition  products  are  different  from  the  sub- 
stances employed  in  the  synthesis. 

The  principle  of  antagonistic  reactions  remains  the 
same  whether  they  take  place  under  the  influence  of 
substances  that  increase  the  velocity  of  the  reactions,  so- 
called  catalyzers,*  or  not.  In  the  organism  we  have 
acting  as  such  catalytic  agents  mostly  ferments,  which 
are  capable  of  acting  only  upon  certain  substances,  and 

*  No  doubt  the  catalyzers  determine  also  the  direction  of  a  reaction,  in 
that  the  reaction  follows  a  qualitatively  different  course  under  the  influence 
of  different  catalytic  substances.  If  one  holds  fast  to  the  above-mentioned 
(Ostwai.d's)  definition  of  catalysis,  then  we  would  be  dealing  in  this 
case  with  several  simultaneously  possible  reactions,  of  which  different 
ones  arc  accelerated  by  different  catalyzers,  while  the  rest  remain  not 
discoverable. 


64  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

playing  a  role,  therefore,  only  when  these  substances 
appear  in  the  organism. 

Such  catalyzers  can  act,  as  was  first  pointed  out  by 
van't  Hoff,  in  two  directions,  depending  upon  the 
relations  existing  between  the  substances  originally  present 
and  those  formed.  In  this  way,  as  has  recently  been 
shown,  amygdalin  cannot  only  be  split  into  amygdalic 
nitrilglucoside  and  glucose  under  the  influence  of  yeast 
maltase,  but  also  be  formed  synthetically  from  these  two 
substances  with  the  help  of  the  same  enzyme.  One  and 
the  same  enzyme  can,  according  to  conditions,  accelerate 
the  one  or  the  other  homodrome  antagonistic  reaction. 
In  the  animal  organism  the  synthesis  of  glycogen  from 
dextrose  and  the  splitting  of  glycogen  into  dextrose  might 
in  part,  at  least,  represent  a  simple  antagonistic  reaction 
governed  by  a  single  enzyme;  while  the  synthesis  of 
starch  in  plants  and  its  diastatic  splitting  into  glucose 
or  maltose  represents  a  heterodrome  antagonistic  reaction 
in  which  the  synthesis  has  the  upper  hand  by  day  and 
the  analysis  by  night. 

It  is  also  possible,  however,  that  two  catalyzers  may 
act  in  such  a  way  upon  a  homodrome  antagonistic  reac- 
tion that  the  one  accelerates  the  conversion  of  the  system 
in  the  one  direction,  while  the  other  does  it  in  the  opposite 
direction.  This  is  the  case  when  the  two  catalyses  go 
hand  in  hand  with  different  equilibrium-points  in  the 
two  reactions  that  constitute  the  simple  antagonistic 
reaction.  An  example  of  this  sort  will  be  given  later. 
The  deposition  and  solution  of  the  calcium  salts  of  the 
bone  represents  a  simple  reversible  reaction  which,  with 
the  aid  of  special  cells,  the  osteoblasts  and  osteoclasts, 
can,  according  to  physiological  needs,  be  divided,  and 


THE  COLLOID.  II.   STATE.  65 

tin'  two  reactions  occur  independently  of  each  other  in 
entirely  separate  localities. 

In  heterodrome  antagonistic  reactions  the  acceleration 
of  the  two  reactions  by  one  and  tin-  same  catalyzer  is 
impossible;  one  catalyzer  can  be  effective  in  only  one  of 
the  two  reactions.  A  reaction  can  take  place  in  one 
direction,  and  at  a  certain  stage — for  example,  after  a 
condensation  or  polymerization  through  one  enzyme — be 
switched  into  another  direction;  or  the  components  of 
the  complex  antagonistic  reaction  may  be  influenced 
through- two  different  catalyzers.  Between  two  catalyzers 
which  displace  the  equilibrium  of  a  homodrome  antag- 
onistic reaction  in  opposite  directions,  there  exists  a  true 
antagonism,  while  a  complex  antagonistic  effect  exists 
where  the  two  components  of  a  heterodrome  reversible 
reaction  are  governed  by  two  catalyzers.  We  may  there- 
fore distinguish  also  between  simple  and  complex  antag- 
onistic ferments. 

A  suitable  example  of  a  heterodrome  antagonistic  re- 
action in  metabolism  is  furnished  by  the  formation  and 
destruction  of  uric  acid  in  the  animal  body.  The  funda- 
mental investigations  of  H.  Wiener  have  thrown  light 
upon  this  subject.  Wiener  found  that  the  "  surviving" 
ground-up  pulp  of  different  animal  organs  has  the  power 
of  both  forming  and  destroying  uric  acid.  In  the  liver 
of  the  ox  the  two  processes  can  take  place  simultaneously 
and  are,  no  doubt,  dependent  upon  the  activities  of  two 
different  catalyzers.  As  the  sensitiveness  of  the  two 
catalytically  acting  substances  toward  heat  is  different, 
the  two  chemical  changes  can  be  separated  from  each 
other,  the  power  to  decompose  uric  acid  being  lost  later 
than  the  power  to   form   it.     That   we  have  to  do  here 


66  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

with  a  heterodrome  reaction  is  indicated  by  the  fact  that 
none  of  the  substances  which  are  formed  in  the  destruc- 
tion of  the  uric  acid  can  be  built  up  into  the  original 
uric  acid. 

It  would  lead  us  too  far  afield  to  discuss  further  the 
fate  of  the  different  substances  that  enter  into  the  metab- 
olism of  the  organism  in  the  light  of  our  conception  of 
antagonistic  reactions  which  can  be  combined  among 
themselves  in  the  greatest  variety  of  ways.  In  the  last 
analysis,  no  doubt,  it  is  because  the  reaction  is  a  hetero- 
drome one  that  no  path  exists  in  the  animal  body  over 
which  urea  can  again  be  "built  up  into  protein. 

The  two  components  of  an  antagonistic  reaction  are 
dependent  upon  each  other  only  in  so  far  as  the  one 
furnishes  the  material  necessary  for  the  other.  We  can 
easily  see  how  in  the  fact  that  they  can  follow  different 
courses  there  resides  the  possibility  that  they  can  take 
place  simultaneously  and  side  by  side.  This  explains 
also  why  ferments  acting  in  opposite  directions  can 
exhibit  their  characteristic  effects  without  the  presence 
of  separating  walls — in  molecular  proximity  to  each 
other,  as  it  were. 

Such  reactions  can  without  mutual  interference  take  place 
side  by  side,  just  as  sound,  light,  and  electric  waves,  or 
currents  of  heat,  electricity,  and  dijjusion,  can  pass  through 
a  medium  simultaneously. 

V. 

The  idea  of  homodrome  and  heterodrome  antagonistic 
reactions,  as  deduced  from  a  consideration  of  changes 
jn  the  colloidal  state  and  in  metabolism,  is  closely  related 


THE  COLLOIDAL   STATE.  67 

to  facts  which  furnish  a  welcome  support  of  this  concep- 
tion in  the  physiology  of  the  senses. 

As  early  as  1865,  through  his  complete  recognition  of  the 
relation  between  the  physical  and  psychic  elements  of  a 
sensation  and  through  the  assumption  that  every  quality  of 
a  sensation  has  lying  at  the  bottom  of  it  a  specific  change 
in  the  substance  of  the  nerve,  which  for  the  same  sensation 
is  the  same,  and  for  similar  sensations  partly  identical. 
E.  Mach  laid  the  foundations  from  which,  through  an 
analysis  of  the  sensations,  a  knowledge  of  the  changes 
that  go  on  in  living  matter  has  been  obtained.  In  his 
hands  and  through  the  work  of  E.  Hering,  who,  some- 
what later  and  independently  of  Mach,  set  up  the  same 
principle  of  research,  this  led  to  a  great  enrichment  of 
the  physiology  of  the  senses.  Upon  these  same  founda- 
tions Hering  has  built  up  his  famous  theories  of  the 
sense  of  light  and  color,  a  theory  of  the  temperature  sense, 
and  finally  a  general  theory  of  the  changes  that  go  on  in 
living  matter.  The  great  and  fruitful  significance  that 
these  principles  possess,  not  only  for  questions  in  the 
physiology  of  the  senses,  but  also  for  general  physiology 
and  for  a  recognition  of  the  aims  and  limits  of  scientific 
research  in  general,  could  only  temporarily  be  belittled, 
through  the  mighty  authority  of  a  Helmholtz.  To-day 
when  this  combat  is  a  thing  of  the  past  and  the  teaching 
of  Mach  and  Hering  has  made  itself  felt  in  the  most 
varied  branches  of  science,  we  recognize  that  in  decades 
general  physiology  has  enjoyed  no  such  significant  increase 
in  enlightenment  as  has  been  furnished  by  the  Mach- 
Hering  analysis  of  the  sensations  and  the  physical  changes 
that  lie  at  the  bottom  of  these  sensations 

We  will  enter  into  this  physic  logy  of  the  senses  only 


68  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

far  enough  to  show  that  it  contains  all  those  elements 
which  we  discovered  in  the  discussion  of  another  subject. 
The  idea  that  antagonistic  reactions  must  be  possible 
in  even  the  smallest  particles  of  protoplasm  we  meet  in 
Hering's  theory  of  the  changes  that  go  on  in  living  matter. 
In  the  discussion  of  assimilation  and  dissimilation,  he 
writes: 

"  But  in  separating  the  mental  conceptions  of  these 
two  processes  we  must  not  be  misled  into  thinking  of 
them  as  two  processes  which,  while  they  go  on  side  by 
side,  are  really  separated,  and  into  imagining  living  sub" 
stance  to  be  within  itself  a  resting  mass  that  on  one  side 
only  analyzes  matter  and  on  the  other  only  synthesizes 
it ;  but  rather  as  a  copper  wire  dipping  with  both  its  ends 
into  copper  sulphate,  which  when  it  is  traversed  by  an 
electric  current  suffers  at  one  end  a  loss  of  copper  by 
going  into  solution,  while  at  the  other  end  it  has  copper 
deposited  upon  it.  We  must  rather  imagine  assimilation 
and  dissimilation  as  two  closely  interwoven  processes  which 
constitute  the  still  unknown  metabolism  of  living  matter, 
and  which  take  place  simultaneously  in  even  the  smallest 
particles  o]  living  matter,  for  living  matter  represents  not 
something  fixed  or  resting,  but  something  more  or  less 
labile." 

The  investigations  of  Hering  on  the  sensations  of 
light  and  color  led  him  to  the  assumption  of  three  kinds 
of  antagonistic  processes  in  the  visual  substance,  corre- 
sponding with  the  three  pairs  of  sensations,  red-green, 
yellow-blue,  and  black-white.  The  red-green  and  the 
yellow-blue  reactions  each  constitute  a  pair  of  antagonists 
which  mutually  destroy  each  other,  so  that  only  the 
simultaneous    black-white    reaction   remains.     Red   and 


THE   COLLOID.  II.   STATE.  69 

green  or  yellow  and  blue  cannot  be  perceived  at  the 
same  time,  while  black  and  white  can  be  perceived  simul- 
taneously and  can  be  mixed  in  different  proportions  in 
the  gray  sensations.  That  we  arc  dealing  in  this  case 
with  two  kinds  of  antagonistic  processes  has  been  suf- 
ficiently  emphasized  by  Hering. 

Macs  has  also  pointed  out  in  a  general  way  the 
essential  difference  between  the  two  kinds  of  antagonistic 
processes  in  his  doctrine  of  the  sensations  of  motion. 
While  criticising  Plateau's  oscillation  theory  Mach 
writes: 

"  When  two  things,  A  and  B,  are  designated  as  positive 
and  negative  with  regard  to  each  other,  one  understands 
thereby  that  A  can,  through  the  addition  of  B,  be  in 
part  or  entirely  destroyed.  This  relation  exists  between 
many  sensations  and  their  after-images,  but  not  be- 
tween all.  It  exists,  for  example,  between  the  percep- 
tion of  a  movement  and  its  after-image,  which  is  an 
entirely  similar  movement,  but  of  an  opposite  character. 
It  does  not  exist,  however,  between  the  sensations  black 
and  white,  of  which  the  one  may  also  be  the  after-image 
of  the  other.  Both  sensations  are  entirely  different  from 
each  other,  and  the  two  together  do  not  annihilate  each 
other,  but  produce,  as  do  two  different  colors,  a  mixed 
color,  namely,  gray.  In  this  case,  therefore,  the  terms 
positive  and  negative  arc  not  appropriately  apjilicd. " 

According  to  our  conception,  those  antagonistic  reactions 
that  behave  as  positive  and  negative  values  are  homo- 
drome,  tin-  other  heterodrome  reactions. 

Nothing  stands  in  the  way  of  regarding  the  individual 
kinds  of  light  as  catalyzers  of  antagonistic  reaction-. 
Corresponding  with  this  idea,  we  would   pronounce  the 


10  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

red-green  reaction  and  the  yellow-blue  reaction  as  homo- 
drome  antagonistic  ones,  the  mobile  equilibria  of  which 
can  be  pushed  in  opposite  directions  under  the  influence 
of  two  catalyzers.  But  these  reactions  may  at  one  time 
take  place  in  the  one  direction,  at  another  in  the  opposite 
direction,  so  that  red  and  green  can  never  be  simultaneously 
discovered  in  a  color,  no  more  than  blue  and  yellow.  The 
black-white  sensation  would,  on  the  other  hand,  represent 
a  heterodrome  antagonistic  reaction  which,  under  the 
influence  of  white  light,  moves  along  one  course,  but  en- 
deavors spontaneously  to  move  back  along  another.  As 
these  oppositely  running  components  of  the  antagonistic 
reaction  can  occur  side  by  side,  black  and  white  can 
be  perceived  simultaneously. 

With  this  we  will  bring  our  consideration  of  antag- 
onistic reactions  in  living  matter  to  an  end.  A  more 
detailed  study  of  the  questions  which  are  involved  is 
reserved  for  a  future  paper. 

If,  in  conclusion,  we  look  back  once  more  over  the 
path  that  has  been  traversed,  every  step  seems  to  indicate 
that  physico-chemical  investigations  of  a  substance  that 
is  closely  related  to  living  matter  are  able  to  throw  much 
light  upon  the  conditions  that  exist  in  living  matter.  In 
fact,  we  see  that  the  experimental  results  obtained  in 
this  way  pass  over  to  meet  those  which  direct  observation 
of  the  changes  that  go  on  in  living  matter  yields. 

Investigations  of  this  kind  are  well  suited  to  show  how 
all  biological  methods  are  of  the  same  value,  in  that 
they  leave  no  room  for  strictly  mechanistic  or  vitalistic 
tendencies.  They  form  a  mighty  support  for  the  true 
scientific  monism.  The  investigator,  however,  they  fill 
with  a  conception  of  those  overpowering  feelings  of  the 


THERAPEUTIC  STUDIES  ON  IONS  7' 

explorer  who  imagines  himself  upon  an  island  until  he 
discovers  a  connection  with  the  scarcely  measurable 
continent  beyond. 

4.  Therapeutic  Studies  on  Ions.* 

"The  acquisition  of  ;i  new  truth  is  like  the  acquisition 
of  a  new  sense,  which  renders  a  man  capable  of  perceiving 
and   recognizing  a   large   number  of  phenomena    that  are 

invisible  and    hidden    from   another,   as  they  were  from  him 
originally.'- — Chemisette  Brieje. 

With  scarcely  more  fitting  words  than  these  of  the  old 
master  Liebig  can  we  characterize  the  increase  in  scien- 
tific knowledge  and  the  establishment  of  new  methods 
of  work  and  points  of  view  for  which  we  are  indebted 
to  the  application  of  the  laws  of  physical  chemistry  to 
questions  in  biology  and  even  in  practical  medicine.  If 
we  try  to  determine,  from  the  varied  and  many  advances 
that  have  been  made,  along  what  lines  these  were  made, 
it  can  be  easily  shown  that  the  application  of  three  es- 
pecially of  the  fundamental  laws  of  physical  chemistry  to 
biological  problems  has  been  most  fruitful.  These  are 
the  law  oj  chemical  mass  action  of  Guldberg  and  Waage, 
which  permits  of  an  insight  into  the  course,  the  velocity, 
and  the  ultimate  equilibrium  of  chemical  reactions;  the 
theory  oj  osmotic  pressure,  which  has  discovered  to  us 
the  common  properties  possessed  by  any  series  of  solutions 
independently  of  the  nature  of  the  dissolved  substances; 
and  the  theory  oj  the  electrolytic  dissociation  oj  certain 
dissolved    substances,    the   foundation   of   which     resides 


*  From  Miinchener  medizinalische  Wochenschrift,  1003,  p.  153.     Ad- 
dress delivered  before  the  K..  k.  Gesellschafl  dei  Aerzte,  Vienna. 


72  PHYSICAL   CHEMISTRY  IN  MEDICINE'. 

in  the  partial  dissociation  into  electrically  charged  ions 
which  salts,  acids  and  bases  suffer  when  dissolved  in 
certain  solvents,  especially  water. 

The  effects  of  salts  within  and  without  the  organism 
must  all  be  treated  from  the  standpoint  of  how  far  the 
electrically  charged  ions  or  the  electrically  neutral  mole- 
cules play  a  part.  Such  an  investigation,  carried  out 
from  both  a  theoretical  and  a  practical  point  of  view,  is 
to  form  the  subject  of  my  address  to-day. 

I. 

It  is  evident  that  there  exist  different  ways  in  which 
the  unknown  pharmacological  properties  of  a  substance 
may  be  studied.  As  least  practical  and  economical  would 
to-day  be  the  attempt  to  employ  the  substance  directly 
in  cases  of  illness.  The  animal  experiment  is  little  better, 
and  is  of  use  only  when  it  is  possible  to  reproduce  the 
disease  artificially  in  a  more  or  less  perfect  way,  as  in 
the  case  of  the  infectious  diseases.  Modern  pharma- 
cology has  been  very  successful  in  predicting  the  nature 
of  the  therapeutic  effect  of  newly  discovered  chemical 
compounds  from  their  chemical  constitution.  There 
exists,  however,  another  way  which,  though  still  but 
little  used,  renders  it  possible  under  suitable  conditions 
to  discover  unsuspected  pharmacodynamic  relations. 
This  is  the  application  of  a  principle  which  I  published 
years  ago,  and  which  has  since  then  rendered  possible 
the  solution  of  difficult  problems  in  physiology.  This 
may  be  called  the  principle  o]  the  manifold  analogies 
which  exist  between  the  changes  in  state  suffered  by  colloids 
and  the  changes   that  take  place  in  living  matter.     In 


THERAPEUTIC  STUDIES  ON  IONS. 


73 


attempting  to  apply  this  principle,  let   us  discuss  first 

of  all  the  mutual  effects  <>f  proteins  and  salts  upon  each 
other. 

As  is  well  known,  proteins  suffer  a  change  in  state  in 
the  presence  of  many  salts — they  are  precipitated  in  solid 
form.  In  the  case  of  the  salts  of  the  alkali  metals  and 
magnesium  this  precipitation  does  not  occur  until  a  cer- 
tain, fairly  high  concentration  has  been  reached.  The 
precipitate  rcdissolves  when  the  solution  is  diluted;  the 
process  is,  in  other  words,  reversible.  We  will  discuss 
first  of  all  the  laws  governing  these  reversible  precipi- 
tations. 

If  the  salts  are  arranged  according  to  their  power  of 
precipitating  protein  fas  determined  by  the  use  of  chem- 
ically equivalent  solutions),  the  following  table  is  ob- 
tained. +  indicates  that  the  protein  is  precipitated,  — 
that  it  is  not,  n.  s.  that  the  salt  has  not  been  studied. 


Cations.     The  precipitating  power  increases- 


I.  Fluoride 

II.  Sulphate 

III.  Phosphate 

IV.  Citrate 

Y.  Tartrate 

VI.  Acetate 

VII.  Chloride..:.... 

VIII.  Nitrate 

IX.  Bromide 

X.  Iodide 

XI.  Sulphocyanate.  . 


I 

2 

3 

4 

Mg 

NH4 

K 

Na 

n.  s. 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

n.  s. 

+ 

+ 

+ 

n.  s. 

+ 

+ 

+ 

n.  s. 

+ 

+ 

+ 

— 

— 

+ 

+ 





+ 

+ 
+ 

n.  s. 

_ 

_ 

_ 

n.  s. 

+ 
n.  s. 
n.  s. 
n.  s. 
n.  s. 

+ 

+ 

+ 
n.  s. 
n.  s. 


For  one  and  the  same  anion  the  precipitating  power 
increases  from  magnesium  toward  lithium,  and  for  each 


74  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

metallic  ion  the  precipitating  power  decreases  in  the 
direction  from  fluoride  toward  bromide.  No  matter  which 
anion  we  take,  therefore,  we  find  that  the  cations  always 
follow  the  same  order  when  arranged  according  to  their 
precipitating  power,  and,  conversely,  that  with  any  cation 
the  anions  always  follow  the  same  order  when  they  are 
arranged  according  to  their  precipitating  power.  This 
law  may  also  be  stated  thus:  The  precipitating  power 
of  a  salt  is  determined  by  the  sum  of  the  powers  of  its 
individual  ions,  which  act  in  large  part  independently 
of  each  other. 

In  what  way,  now,  do  the  anions  and  the  cations  act? 
It  might  be  thought,  first  of  all,  that  both  the  metallic 
and  the  acid  ions  of  a  salt  have  a  specific  precipitating 
effect,  and  that  the  sum  of  these  two  positive  values 
constitutes  the  precipitating  power  of  an  electrolyte. 
According  to  this  conception,  the  precipitating  power 
of  sodium  acetate  would  be  made  up  of  the  precipitating 
effect  of  the  sodium  ion  plus  that  of  the  acetic  acid  ion. 
Many  salts  are  known,  however,  which  in  spite  of  their 
ready  solubility  precipitate  protein  in  no  concentration, 
so  that  the  above  explanation  does  not  hold  at  all  in 
these  cases.  Ammonium  acetate,  for  example,  does  not 
precipitate  protein  in  any  concentration,  while  the  acetic 
acid  ion  of  sodium  acetate  and  the  ammonium  ion  of 
ammonium  sulphate  are  both  strong  precipitants.  An 
explanation  without  contradictions  is  offered  by  the  fol- 
lowing experimentally  supported  conception.  Only  the 
metallic  ions,  or  cations,  act  as  the  precipitating  constituents 
of  the  salts,  and  the  oppositely  charged  anions  inhibit 
this  precipitating  property. 

It  is  self-evident  that  only  those  salts  will  precipitate 


THERAPEUTIC   STUDIES   ON  IONS.  75 

protein  in  which  the  precipitating  power  of  the  cations 
exceeds  the  inhibiting  effects  of  the  anions.  Lit  us 
study  the  above  table  with  this  idea  in  mind.     The  table 

shows  along  the  horizontal  the  metallic  ions  arranged 
in  the  order  of  their  precipitating  power,  along  the  vertical 
the  anions  arranged  in  the  order  of  their  inhibiting  effect. 
It  is  now  at  once  intelligible  why  sodium  nitrate,  with 
its  powerful  precipitating  sodium  ion,  coagulates  protein, 
while  the  weaker  precipitants,  K,  NH4,  and  Mg  ions, 
are  overcome  in  their  effects  by  the  antagonistic  NO3 
ion.  Only  the  lithium  salt  of  the  bromides  precipitates, 
and  so  we  might  go  on. 

The  table  discloses  yet  other  facts.  If  it  is  true  that 
the  effect  of  salts  upon  proteins  is  determined  through 
the  antagonistic  properties  of  their  ions,  then  there  must 
exist  not  only  salts  which  precipitate  protein  or  are  in- 
different, but  also  such  as  prevent  precipitation  or  dis- 
solve already  existing  precipitates.  Observation  has  con- 
firmed this  important  conclusion.  When  it  has  been 
determined  experimentally  that  a  certain  salt  behaves 
indifferently  toward  protein,  then  it  will  be  found  that 
all  other  salts  found  to  the  right  and  above  the  point 
occupied  by  this  salt  in  the  table  will  have  precipitating 
properties,  while  salts  found  to  the  left  and  below  this 
point  will  inhibit  protein  precipitation.  The  fact  that 
it  has  been  the  protein-precipitating  salts  which  have 
until  now  chiefly  held  the  attention  of  investigators  has 
prevented  the  recognition  of  this  conspicuous  phenom- 
enon. 

An  experiment  will  best  illustrate  what  has  been  said. 
Each  of  this  series  of  test  tubes  contains  the  same  amount 
of  solvent,   and   neutral   potassium  tartrate  in  sufficient 


76  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

amount  to  precipitate  protein.  With  the  exception  of  the 
first  tube,  they  all  contain  in  addition  different  ammonium 
salts  in  chemically  equivalent  concentrations  arranged 
in  the  order  given  in  the  table.  As  can  be  readily  seen, 
the  fluoride  and  sulphate  increase  the  precipitate,  the 
chloride  is  practically  indifferent,  while  the  bromide, 
iodide,  and  sulphocyanate  hinder  in  increasing  degree 
the  coagulation  through  the  potassium  tartrate. 

From  a  large  number  of  similar  experiments  it  has 
been  possible  to  deduce  the  following  laws,  which  will 
be  utilized  as  the  foundation  for  what  is  to  follow: 

i.  The  effect  of  a  salt  upon  a  protein  is  made  up,  in 
the  main,  of  the  algebraic  sum  of  the  effects  of  the  in- 
dividual ions. 

2.  Anions  and  cations  antagonize  each  other — the 
cations  precipitate,  the  anions  inhibit  precipitation;  there 
results  in  this  way  a  definite  grouping  of  the  ions  according 
to  the  intensity  of  their  actions. 

I  wish  to  add  that  an  analogous  table  of  ions  has  been 
constructed  for  the  salts  of  the  alkaline  earths  and  the 
heavy  metals,  though  an  investigation  of  the  protein 
precipitates  brought  about  by  these  salts  is  attended 
by  many  complicating  circumstances. 

II. 

With  the  exception  of  the  beautiful  studies  of  Dreser 
on  the  toxicity  of  mercury  salts  and  scattered  investiga- 
tions on  the  effects  of  electrolytes  on  unicellular  organisms, 
there  exist  but  few  attempts  to  apply  the  ionic  theory 
to  the  pharmacology  of  salts.  One  cannot  even  say  that 
the  conception  of  the  general  effects  of  salts  the  basis 


THERAPEUTIC  STUDIES   ON  IONS.  77 

of  which  is  often  sought  in  the  theory  of  osmotic  pressure 
is  entirely  clear.  The  introduction  of  the  ionic  theory 
may  perhaps  be  the  first  means  of  bringing  a  better 
understanding  into  this  field  also.  Under  these  conditions 
it  is  readily  intelligible  that  from  a  classification  of  the 
ions  won  through  a  study  of  the  changes  in  state  of  pro- 
teins only  broad  generalizations  can  be  made.  These 
have,  however,  shown  themselves  valuable  in  pointing 
out  the  direction  which  further  investigations  must  take. 

The  relation  between  the  cathartic  effects  of  salts  and 
their  power  to  precipitate  protein  has  been  recognized 
for  a  long  time,  more  especially  through  the  fundamental 
investigations  of  Hofmeister.  If  we  bear  in  mind  what 
has  been  said  above,  that  the  power  of  precipitating  pro- 
tein is  a  property  of  the  metallic  ions,  then  we  will  also 
have  to  attribute  the  transitory  purgative  action  of  the 
alkali  salts  to  their  cations.  This  faculty  is,  in  fact, 
seen  to  reappear,  only  accentuated  to  an  extreme,  in  the 
case  of  the  heavy  metals,  which,  it  is  well  known,  are 
able  to  coagulate  protein  in  even  the  weakest  concen- 
tration. The  mild  contractile  and  purgative  action  cor- 
responds in  the  latter  case  to  the  erosion  and  severe 
gastro-enteritis  of  the  toxic  picture.  Most  of  the  metallic 
ions  also  influence  more  or  less  markedly  the  irritability 
of  the  nervous  system,  the  heavy  metals  producing  in- 
flammation and  degeneration. 

The  anions  also  appear  as  mighty  carriers  of  pharma- 
cological properties.  This  is  especially  true  of  the  end 
members  of  one  scries — the  nitrates,  bromides,  and  iodides. 
They  are  all  readily  absorbed  and  bring  about  a  lower- 
ing of  the  blood-pressure.  The  Br  ion  shows  a  much- 
utilized  sedative  action,  while  the  I   ion  belongs  among 


78  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

those  therapeutic  agents  that  have  a  multiplicity  of 
effects.  Besides  its  specific  relation  to  the  metabolism 
of  the  thyroid  gland,  it  is  employed  for  its  power  of 
lowering  blood-pressure  in  arteriosclerosis  and  for  its 
absorptive  effect  upon  the  most  varied  products  of  chronic 
inflammation,  more  especially  the  late  forms  of  syphilis. 
Readily  as  one  can  recognize  in  these  general  consid- 
erations how  the  effects  of  the  ions  of  a  salt  are  independent 
of  each  other,  and  how  there  exists  an  antagonism  between 
cations  and  anions,  the  grouping  given  above  suggests 
something  which  leads  us  still  further.  Even  if  we  pro- 
ceed most  carefully  in  the  extension  of  our  analogy,  it 
must  be  apparent  to  every  one  that  the  sulphocyanate 
ion,  which  antagonizes  precipitation  most  powerfully, 
constitutes  the  end  member  of  a  series  of  pharmaco- 
logically most  active  subsfances,  and  so  the  question 
arises  whether  this  ion  does  not  possess  some  peculiar 
medicinal  effect.  The  direction  in  which  such  an  effect 
.is  to  be  sought  is  also  indicated  by  the  position  of  this 
ion  in  our  scale. 

III. 

So  far  as  I  know,  there  exist  no  therapeutic  experi- 
ments on  sulphocyanate  compounds.  At  any  rate, 
nothing  definite  can  be  found  in  large  handbooks  on 
therapy  or  in  very  complete  text-books  on  pharmacology. 
The  role  of  sulphocyanate  in  metabolism  has  absorbed 
the  attention  of  many  investigators  since  its  discovery 
as  a  normal  constituent  of  the  saliva  by  Treviranus, 
Tiedemann  and  Gmeitn.  As  Gscheidlen  and  Munk 
discovered  independently  of  each  other,  sulphocyanate 


THERAPEUTIC  STUDIES  ON  IONS.  79 

occurs  also  in  the  urine.  The  sulphocyanate  of  the 
urine  might  well,  however,  be  absorbed  from  the  saliva, 

for,  according  to  Gscheidlen,  it  disappears  entirely  from 
the  urine  of  the  dog  as  soon  as  the  excretory  ducts  of  the 
salivary  glands  arc  turned  outward. 

As  to  where  in  the  body  sulphocyanate  is  formed,  is 
still  unsettled;  we  know  something,  however,  of  the 
manner  in  which  it  is  produced.  S.  Lang  has  shown 
that  all  cyanides  and  nitrils  are  converted  into  sulpho- 
cyanates  in  the  organism.  This  change  probably  occurs 
through  a  process  of  association  with  the  neutral  sulphur 
of  the  proteins,  for  I  succeeded  in  bringing  about  such 
a  synthesis  years  ago  in  Hofmeister's  laboratory  with 
proteins  and  their  derivatives,  provided  they  had  not  first 
been  robbed  of  their  readily  removable  sulphur  group. 

Recent  experiments  of  Bruylants  indicate  that  a 
relation  exists  between  the  metabolism  of  the  sulpho- 
cyanates  and  that  of  the  purin  bodies.  In  an  investiga- 
tion characterized  by  originality  and  far-sightedness,  and 
carried  on  in  1853  in  the  Wiener  Institut  fur  patho- 
logische  Chemie,  Kletzinsky  made  valuable  contribu- 
tions to  our  knowledge  of  the  excretion  of  sulphocyanate 
in  healthy  and  diseased  su  jeets,  which  have  in  the  main 
been  corroborated,  most  recently  by  Grober.  The 
intoxication  after  large  subcutaneous  doses  of  sulpho- 
cyanate was  studied  twenty-seven  years  ago  by  Paschkis 
on  dogs,  rabbits,  and  frogs.  Valuable  experiments  on 
the  effect  of  sulphocyanate  on  the  metabolism  of  man 
and  animals  have  in  recent  years  been  made  by  Treupel 
and  Edinger.  Muck  recently  discovered  sulphocyanate 
as  a  separate  secretory  product  in  the  conjunctival  and 
olfactory  secretions. 


8o  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

Of  primary  interest  for  us  is  the  proof  that  iodine  and 
sulphocyanate  are  excreted  in  the  same  places  in  the 
organism,  that  sulphocyanates  do  not  pass  through  the 
body  in  even  small  doses  without  altering  the  metabolism, 
and  that  a  single  dose  of  sulphocyanate,  as  discovered 
by  Munk  in  1877,  still  brings  about  an  increased  secretion 
of  this  substance  a  week  later.  As  was  recognized  by 
even  the  earliest  workers  in  this  field,  the  excretion  of 
sulphocyanate  is  decreased  when  iodine  is  taken,  and* 
completely  stopped  when  iodism  is  produced.  When 
this  condition  exists,  Grober  found  that  even  concen- 
trated saliva  gives  no  sulphocyanate  reaction. 

We  are  acquainted,  therefore,  with  isolated  facts  in 
the  physiology  and  the  pathology  of  sulphocyanate  ex- 
cretion which  indicate  that  a  relationship  exists  between 
sulphocyanates  and  iodides. 

IV. 

The  following  report  on  therapeutic  experiments  with 
sulphocyanate  ions  is  based  upon  a  rather  small  amount 
of  material.  If  we  exclude  the  orientation  experiments 
to  determine  how  much  of  the  substance  can  be  borne 
and  how  it  is  excreted,  there  are  thirty-five  cases  in  all 
in  which  careful  observations  were  made  and  registered, 
the  possibility  that  other  curative  agencies  were  simul- 
taneously active  taken  into  consideration,  and  these 
results  controlled  as  far  as  possible  by  omitting  the 
sulphocyanate  or  using  other  remedies.  Since  sodium 
ions  are,  as  far  as  we  know,  the  most  indifferent  of  the 
metallic  ions  from  a  pharmacological  standpoint,  sodium 
sulphocyanate  was  employed,  and  this  in  the  maximal 


THERAPEUTIC  STUDIES   ON  IONS.  8 1 

daily  dose  of  one  gram.    'The  excretion  of  the  .-ulpho- 
cyanate  was  studied  in  the  saliva  and  urine. 

The  existence  of  a  sedative  action  was  tested  on  a 
series  of  neuroses  and  organic  nervous  diseases  in  which 
the  signs  of  an  increased  excitability,  such  as  fear,  irri- 
tability, sleeplessness,  increased  reflexes,  tremors,  etc., 
existed.  Ten  cases  in  all  were  studied:  2  cardiac  neuroses, 
with  signs  of  general  neurasthenia,  3  neurasthenics,  2 
general  paretics,  and  1  tabes  dorsalis,  with  increased 
irritability,  and  2  climacteric  neuroses.  In  nine  of  the 
cases  positive  results  were  obtained.  Within  two  to  five 
days  the  patients  became  much  quieter,  and  with  further 
use  of  the  drug  a  very  decided  improvement  in  even  the 
most  disturbing  symptoms  took  place.  The  fear,  rest- 
1  ss  -hep,  headache,  and  dizziness  became  less,  the 
troublesome  congestions  of  the  climacteric  women  passed 
away,  and  a  sense  of  rest  repeatedly  took  the  place  of 
weariness  in  the  patient.  Only  in  one  case  did  the 
original  neurasthenic  symptoms  return  after  being  absent 
for  some  days.  These  were  connected  with  periodic 
pains  in  the  splenic  region,  which  radiated  toward  the 
epigastrium,  the  pathology  of  which  remained  obscure. 
A  subsequent  use  of  bromides  was  also  without  effect 
in  this  case.  The  fact  that  the  symptoms  of  increased 
excitability  in  organic  and  functional  nervous  diseases 
began  to  disappear  a  short  time  after  taking  sulpho- 
cyanatc  and  continued  to  improve  as  time  went  on,  that 
the  old  symptoms  reappeared  when  the  drug  was  no 
longer  given,  especially  when  it  was  taken  away  shortly 
after  its  use  had  been  begun,  that  previous  indifferent 
methods  of  treatment  had  brought  no  greal  change  in 
the   patients'   condition,   and   that,   finally,    unprejudiced 


82  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

observers  as  well  as  the  patients  themselves  felt  convinced 
of  the  immediate  good  effects  of  the  drug,  seems  to  justify 
the  conclusion  that  sulphocyanate  possesses,  as  a  rule,  a 
well-marked  sedative  action  upon  the  pathologically 
excited  nervous  system. 

The  experiments  with  sulphocyanates  were  then  ex- 
tended to  a  group  of  diseases  which  have  one  symptom 
in  common,  namely,  an  increase  in  the  blood-pressure. 
These  included  arteriosclerosis,  aortic  insufficiency,  and 
chronic  nephritis.  From  the  large  number  of  patients 
with  circulatory  disturbances  in  Professor  v.  Basch's 
wards,  eleven  cases  of  arteriosclerosis  were  chosen,  nine  of 
which  showed  tortuosity  and  great  pulsation  of  the  blood- 
vessels, hypertrophy  of  the  left  ventricle,  accentuation  of 
the  second  aortic  sound  (usually  with  an  increase  in  the 
intensity  of  the  apex-beat),  and  marked  increase  in  the 
blood-pressure,  besides  a  number  of  subjective  symptoms. 
These  consisted  of  pains  in  the  chest,  a  feeling  of  pressure  • 
and  shortness  of  breath  on  exertion,  especially  after  meals 
or  at  night,  a  sense  of  fear  and  disturbed  sleep,  while 
two  of  them  showed,  in  addition,  attacks  of  dizziness 
and  ringing  in  the  ears. 

Corresponding  with  the  uniformity  in  clinical  material, 
the  drug  also  showed  a  uniformity  in  action.  The  sense 
of  fear  disappeared;  the  attacks  diminished  within  a  few 
days,  to  return  later  only  under  special  provocation. 
Disturbances  which  had  existed  for  months,  such  as 
ringing  in  the  ears  and  attacks  of  dizziness  disappeared, 
not  to  return.  In  most  of  the  patients  systematic  blood- 
pressure  determinations  were  made  with  v.  Basch's 
sphygmomanometer  by  Dr.  S.  Kornfeld,  who  very 
generously  gave  me  the  benefit  of  his  years  of  experience 


THERAPEUTIC  STUDIES   ON  IONS.  83 

in  this  field.  A  steady  drop  in  blood-pressure,  amounting 
from  10  to  25  per  cent,  of  the  original  value,  could  beob 
served  within  a  few  days  in  all  the  cases  studied.  As  soon 
as  the  drug  was  stopped  the  blood-pressure  rose  again, 
often  to  the  original  height  within  three  to  four  days.  Ac- 
companying this,  there  was  also  a  return  of  some  of  the 
previous  symptoms.  Of  interest  are  two  further  cases 
of  sclerosis  of  the  larger  arteries.  One  of  these  was  a 
female  patient  with  sclerosis  of  the  abdominal  aorta,  which 
could  with  its  large  branches  be  readily  palpated  and 
which  gave  rise  to  severe  attacks  of  pain  in  the  abdomen ; 
the  other,  a  woman  with  all  the  signs  of  an  advanced 
arteriosclerosis,  who  had  suffered  for  months  with  pain 
and  weakness  in  the  right  arm,  which  appeared  on  the 
slightest  exertion  or  when  the  arm  was  allowed  to  hang 
by  the  side  for  some  time.  Besides  this  there  existed 
a  so  intense  and  painful  sense  of  cold  in  the  diseased 
extremity,  which  corresponded  with  a  very  noticeable 
decrease  in  the  temperature  of  the  skin,  that  the  lower 
arm  and  the  right  hand  had  always  to  be  wrapped  in 
thick  cloths.  After  a  test  had  been  made  with  sodium 
bromide  and  aspirin,  and  these  had  proved  entirely  with- 
out effect,  the  pains  diminished  very  markedly  after  an 
eight  days'  use  of  diuretin.  After  taking  sodium  sulpho- 
cyanate  for  a  number  of  weeks  the  sensation  of  cold 
gradually  disappeared,  the  hand  no  longer  needed  to 
be  wrapped  in  cloths,  and  the  weakness  in  the  ex- 
tremity disappeared  sufficiently  so  that  the  patient,  who 
had  been  under  observation  for  eight  months,  was  able 
to  do  light  work  about  the  house.  The  blood-pressure 
fell  during  this  time  from  210  to  160  mm.  of  mercury. 
The  patient  with  arteriosclerotic  pains  in  the  splanchnic 


84  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

region  was  much  relieved,  especially  during  the  first 
weeks,  by  the  sulphocyanate  treatment,  while  other 
methods  had  been  without  effect.  Whenever  the  sulpho- 
cyanate administration  was  interrupted,  the  blood-pressure 
rose,  and  with  it  returned  the  old  symptoms. 

Besides  the  decrease  in  the  blood-pressure,  a  sedative 
action  may  also  play  a  role  in  the  medicinal  effects  of 
sulphocyanates.  It  is  possible  that  yet  another  factor 
plays  a  role,  which  can,  however,  only  be  touched  upon 
here.  In  investigations  carried  on  during  the  past  two 
years  with  Dr.  Peter  Rona  on  the  relation  between  the 
effects  of  iodides  and  sulphocyanates  and  the  effects  of 
salts  of  the  heavy  metals  and  the  alkaline  earths,  the 
following  has  been  found: 

It  has  been  definitely  established  through  exact  ob- 
servation and  experiment  that  the  iodides  bring  about 
and  favor  the  excretion  of  the  ions  of  the  heavy  metals, 
such  as  lead  and  mercury,  in  cases  of  chronic  intoxication. 
The  explanation  of  this  fact,  which  has  been  utilized 
therapeutically,  has  been  sought  in  the  formation  of 
soluble  albuminates,  which  the  iodides  have  been  sup- 
posed to  bring  about. 

When  quantitative  experimens  on  protein  precipita- 
tion are  made,  it  is  found  that  the  heavy  metals  show 
at  first  a  rapid  increase  in  the  precipitation  value,  with 
an  increase  in  the  concentration  of  the  salt,  which  later, 
however,  as  in  the  case  of  zinc,  gradually  falls  to  zero. 
When  the  concentration  of  the  salt  is  still  further  increased, 
a  precipitate  appears  a  second  time,  which  is  very  heavy 
and  which  also  is  again  soluble.  Curves  in  which  the 
ordinates  indicate  the  degree  of  precipitating  power,  the 
abscissas  the  amount  of  salt  of  a  heavy  metal  employed, 


THERAPEUTIC  STUDIES   ON  IONS.  85 

can  be  constructed  to  give  a  graphic  survey  of  these 
relations.  Such  precipitation  curves  suffer  a  great  change 
upon  the  addition  of  iodides  or  sulphocyanates.  If  the 
ions  of  the  heavy  metals  are  present  in  a  low  concentra- 
tion, the  precipitation  of  the  protein  is  prevented  alto- 
gether; if  present  in  larger  amounts,  the  protein  precipita- 
tion is  markedly  increased.  In  the  case  of  living  animals 
only  the  former  possibility,  that  of  the  presence  of  but 
a  low  concentration  of  poisonous  ions,  comes  into  con- 
sideration. The  iodides  and  still  more  the  sulphocyanates 
do  in  fact  act  under  these  circumstances  as  substances 
which  favor  the  formation  of  readily  soluble  protein 
compounds,  through  which  an  elimination  of  the  heavy 
metals  is  greatly  aided.  Conditions  in  the  test-tube  and 
in  the  animal  body  are  here,  in  the  main,  identical. 

The  relation  of  the  metals  calcium,  barium,  and  stron- 
tium to  the  proteins  is  somewhat  different,  a  fact  of 
interest  because  of  the  important  role  of  the  calcium 
ions  in  physiological  and  pathological  questions.  These 
metals  stand  in  many  ways  between  the  alkali  metals 
and  the  true  heavy  metals.  They  have,  in  common  with 
the  former,  a  high  precipitation  limit;  with  the  latter,  the 
fact  that  the  combination  between  protein  and  metal  is  a 
firm  one,  and  once  produced  continues  even  upon  the  ad- 
dition of  water  to  the  solution.  The  power  of  depressing 
most  markedly  the  precipitation  limit  of  the  earthy  metals 
is  possessed  to  a  slight  degree  by  the  Br  ion,  in  greater 
degree  by  the  I  ion,  and  most  powerfully  by  the  sulpho- 
cyanate  ion.  In  the  presence  of  sulphocyanate  ions, 
calcium,  strontium,  and  barium  chloride  will  precipitate 
protein  when  present  in  simple  normal  solution  and  even 
below  this,  while  under  ordinary  circumstances  the  two 


S6  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

latter  will  not  coagulate  in  any  concentration,  and  calcium 
chloride  only  when  present  in  nine  times  the  concentra- 
tion given  above.  This  formation  of  a  solid  protein 
compound  is  always  preceded  by  a  state  in  which  an 
intimate  combination  between  the  protein  and  the  metallic 
ion  occurs  even  before  the  precipitation  limit  is  reached. 
It  can  readily  be  seen  that,  through  the  establishment  of 
a  firmer  combination  between  protein  and  calcium  ions 
in  the  presence  of  a  few  iodide  or  sulphocyanate  ions, 
the  formation  of  other  insoluble  calcium  salts  can  be 
inhibited,  and  the  excretion  of  calcium  be  increased  in 
this  way.  The  therapy  of  arteriosclerosis  has  within 
recent  years  been  directed  in  no  small  degree  against  the 
calcification  process  itself.  It  seems  to  me  that  what 
has  been  said  above  serves  as  a  theoretical  basis  for  the 
clinical  experience  of  the  best  observers  in  this  field,  that 
the  continued  use  of  iodides  is  able  to  retard  the  course  of 
arteriosclerosis.  For  reasons  which  will  become  clearer 
later,  the  use  of  sulphocyanates  in  these  cases  would 
represent  a  therapeutic  advance. 

To  the  series  of  cases  of  arteriosclerosis  there  belong 
two  cases  of  aortic  insufficiency  with  palpitation,  dizzi- 
ness, headache,  a  feeling  of  fear,  and  increased  blood- 
pressure.  In  one  of  these  permanent  relief  from  all 
symptoms  was  achieved,  in  the  other  a  temporary  one, 
as  the  therapy  had  to  be  interrupted  after  eight  days. 

Four  patients  with  chronic  Bright's  disease,  hyper- 
trophy of  the  heart,  and  pallor  showed  a  rapid  better- 
ment of  their  subjective  symptoms,  consisting  of  back- 
ache, neuralgias,  and  sleeplessness,  when  put  on  a  milk 
diet  and  sulphocyanate.  Without  attributing  the  better- 
ment to  the  sulphocyanate,  it  could  be  shown  in  these 


THERAPEUTIC  STUDIES   ON  IONS  87 

cases  that  an  existing  chronic  albuminuria  dors  not 
contraindicate  the  use  of  the  drug. 

My  Last  observations  are  taken  from  a  group  of  patients 
with  syphilitic  headaches — two  men  and  two  women. 
In  the  men  there  was  a  history  of  syphilitic  infection;  in 
the  women  abortions  and  still- births  had  occurred.  One 
man  and  one  woman  had  a  year  previously  suffered  from 
the  same  symptoms,  which  had  promptly  disappeared 
after  the  use  of  iodides,  and  only  after  these.  The  head- 
aches were  in  all  cases  very  severe,  and  in  three  of  them 
typically  nocturnal  in  character,  particularly  during  the 
weeks  when  this  symptom  first  developed.  Sensitiveness 
of  the  skull  upon  percussion  also  existed. 

The  syphilitic  character  of  the  pains  was  therefore 
definitely  established  in  these  cases,  so  far  as  this  is 
clinically  possible.  This  diagnosis  was  further  strength- 
ened by  the  uselcssness  clinically  of  physical  healing 
methods  and  antincuralgic  remedies. 

The  effect  of  the  sulphocyanate  in  these  cases  was  so 
prompt  and  so  clearly  beneficent,  even  in  the  first  few 
days  after  administration,  that  its  medicinal  properties 
cannot  be  doubted.*  The  effect  upon  the  patients 
proved  in  all  cases  to  be  a  lasting  one.  The  two  patients 
who  had  for  similar  symptoms  previously  undergone  a 
treatment  with  iodides  agreed  that  the  feeling  of  relief 
had  this  time  come  much  more  promptly.  In  one  of 
the  patients,  who  could  tolerate  drugs  only  badly  and 
who  had  a  year  previously  suffered  from  severe  iodism, 


*  I  do  not,  of  course,  on  the  basis  of  these  few  observations  on  a 
special  form  of  late  syphilis,  want  to  look  upon  the  question  of  the 
specific  effects  of  a  sulphocyanate  therapy  in  syphilis  as  settled. 


88  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

the  sulphocyanate  was  administered  in  two  small  enemas 
daily. 

This  constitutes  a  summary  of  my  experiences  thus 
far.  They  were  obtained  for  purposes  of  general 
orientation  on  patients  of  whom  each  group  presented  a 
great,  almost  monotonous  similarity  in  symptoms.  When 
the  careful  choice  of  cases  is  taken  into  consideration, 
it  can  scarcely  seem  strange  that  the  effect  of  the  drug 
should  have  been  so  uniform.  In  passing  it  must  have 
been  apparent  what  small  doses  of  sodium  sulphocyanate 
proved  remedially  effective.  The  explanation  of  this 
fact  lies  in  part  in  the  low  molecular  weight  of  the  sub- 
stance, fcr  i.o  gram  sodium  sulphocyanate  is  equal  to 
2.15  grams  sodium  bromide  or  2.82  grams  sodium 
iodide. 

But  a  close  relationship  between  these  substances 
shows  itself  not  only  in  the  harmony  of  their  advantages, 
but  also  in  the  harmony  of  their  disadvantages.  There 
exists  a  sulphocyanate  acne  and  a  sulphocyanate  rhinitis. 
The  latter  is  the  commoner.  Twice  a  mere  sugges- 
tion of  it  occurred,  in  one  of  these  cases  only  once  toward 
evening.  In  two  other  cases  copious  secretion  from 
the  nose  and  eyes  set  in,  which  disappeared,  however, 
within  two  to  three  days  after  the  administration  of 
sulphocyanate  was  stopped.  In  only  one  patient  with  a 
sensitive  skin,  which  had  some  months  previously  been 
the  seat  of  a  bromide  exanthem,  a  sulphocyanate  acne 
appeared,  consisting  of  small  nodules,  most  numerous 
in  the  face  and  sparingly  distributed  over  the  trunk  and 
extremities,  which  did  not,  however,  give  any  further 
trouble.  It  disappeared  a  few  days  after  the  medication 
was  stopped.     Gastric  disturbances  never  appeared,  even 


THERAPEUTIC   STUDIES    ON  IONS  89 

after  the  remedy  had  been  used  for  months.  While  a 
great  similarity,  in  part  even  an  identity,  seems  to  exist 
between  the  iodides  and  the  sulphocyanates,  the  latter 
do  not  possess  the  specific  effect  upon  the  thyroid  gland. 

The  use  i  the  drug  even  for  months  docs  not  affect  a 
parenchymatous  goitre.  This  fact  might  well  at  times 
prove  of  therapeutic  advantage. 

Therapeutics  still  continues  to  count  the  salts  among 
the  "alterants"  and  the  "resolvents."  Both  of  these 
properties  of  "changing  the  course  of  a  disease"  and 
"  bringing  about  a  resolution"  the  sulphocyanatc  ions 
possess  in  rich  part,  as  shown  by  our  own  observations. 
From  the  versatility  and  intensity  of  their  action  we  are 
presumably  correct  in  putting  them  beside  the  iodide  ions. 

I  do  not  wish  to  bring  this  paper  to  a  close  without 
adding  a  few  general  remarks  on  the  principle  which 
prompted  it. 

This  leads,  first  of  all,  to  a  conception  of  the  way  in 
which  the  salts  act  upon  the  organism,  which,  though 
still  hypothetical,  encounters  at  present  nothing  which 
speaks  against  it.  Just  as  a  large  group  of  non-ionized 
narcotics  bear  an  intimate  relation,  according  to  H. 
Meyer's  and  Overton's  beautiful  discoveries,  to  the 
lipoids  of  the  cell,  the  ionized  compounds  might  find 
their  point  of  attack  in  the  protein  constituents  of  the 
protoplasm.  A  difference  in  the  distribution,  or  a  re- 
placement of  the  normal  ions  of  the  cell,  would  be  con- 
nected with  changes  in  the  state  of  the  colloids  and  con- 
sequently also  changes  in  function.  If  the  application 
of  our  principle  extend-,  on  the  one  hand,  almost  to  the 
chain  of  psychophysi  al  processes,  it  has  its  limitations, 


9°  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

on  the  other,  which  are  inherent  in  the  nature  of  such  a 
method  itself. 

When  we  speak  of  the  great  analogy  between  changes 
in  state  in  organic  colloids  and  life  phenomena,  we  are 
dealing,  to  use  the  words  of  Maxwell,  "  with  that 
partial  similarity  between  the  laws  of  one  series  of  phe- 
nomena and  those  of  another,  in  consequence  of  which 
the  one  comes  to  illustrate  the  other. "  Besides  a  limited 
identity,  extensive  differences  may  therefore  exist,  many 
of  which  are  still  beyond  our  understanding.  This  holds 
also  for  the  great  differences  known  to  exist  in  the  toxicity 
of  ions  in  animal  experiments.  We  are  at  present  still 
much  inclined  to  attribute,  qualitatively  at  least,  great 
importance  to  the  value  of  animal  experiments  for  settling 
such  a  question  as  the  one  before  us.  This  we  do  un- 
justly, I  believe.  Clinical  therapeutic  experience  must  be 
gotten  by  itself.  The  animal  experiment  brings  in  this 
case  also  only  an  analogy;  at  the  best  it  serves  only  to 
stimulate  further  work. 

5.  On  the  Relation  between  Phys*co-chemical  Properties 
and  Medicinal  Effects.* 

In  the  consideration  of  questions  in  pharmacody- 
namics, from  the  point  of  view  of  physical  chemistry,  a 
scarcely  measurable  field  lies  before  us,  into  only  a  small 
part  of  which,  however,  paths  lead  at  present.  If  under 
these  conditions  I  attempt  to  speak  before  a  body  of 
clinical  men  on  some  questions  which  belong  in  this 
realm  and  which  have  interested  me  for  several  years,  I 

*  From  Verhandlungen  des  XXI.  Congresses  fur  innere  Medicin 
in  Leipzig,  1904. 


PHYSICO-CHEMICAL   PRi  )PERTIES.  91 

can  give  many  good  reasons  for  doing  so.  A^  is  evident  ed 
by  the  studies  of  11.  Meyer  and  <  >verton  on.  the  theory 
of  narcosis,  and  by  the  work  of  Straub  on  the  tenability 
of  the  law  of  mass  action  for  the  distribution  of  certain 
poisons  in  the  organism,  so  our  work,  too,  has  clearly 
shown  that  only  the  use  of  physico-chemical  methods 
renders  possible  a  deeper  understanding  of  medicinal 
effects.  To  this  there  comes  the  well-founded  feeling 
that  in  this  way  explanations  of  the  nature  of  the  im- 
portant phenomena  accompanying  constitutional  changes 
may  also  be  obtained,  a  problem  which  has  long  been 
a  favorite  one  with  the  internal  clinicist. 

This  paper  will  be  limited  to  a  discussion  of  the  role 
of  ions,  those  electrically  charged  dissociation  products 
of  acids,  bases,  and  salts  which  are  produced  when  these 
substances  arc  dissolved  in  water.  We  know  that  the 
mineral  constituents  of  the  body  are,  in  the  concentration 
in  which  they  are  present,  almost  completely  dissociated. 
This  is  true  also  of  the  metallic  and  alkaloidal  salts 
which  are  introduced  into  the  body  for  medicinal  pur- 
poses. Other  pharmacologically  active  substances  which 
scarcely  ionize  on  solution  in  water,  such  as  the  esters, 
may  be  converted  into  ionizable  compounds  in  the  bodv. 
Because  of  this  many-sided  importance  of  the  omni- 
present ions,  it  seemed  of  value  first  of  all  to  get  an 
experimentally  demonstrable  conception  of  the  mode  of 
action  of  the  ions  in  the  animal  body.  Of  all  the  con- 
stituents of  the  protoplasm,  the  proteins  show  the  most 
intimate  relation  to  the  salts.  Their  most  varied  changes 
in  state,  such  as  solution,  precipitation,  and  coagulation 
through  heat,  arc  all  connected  with  the  cooperation  of 
salts,  and  it  seemed  necessary,  therefore  to  obtain   first 


92  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

of  all  a  more  intimate  knowledge  of  the  significance  of 
the  ions  for  these  changes  in  state. 

The  neutral  salts  of  ammonium,  magnesium,  and  the 
alkali  metals  are  best  adapted  to  such  a  study,  as  the  pro- 
tein precipitates  produced  by  them  can  be  reobtained  in  an 
almost  unaltered  condition  through  dialysis  of  the  salt. 
The  most  important  laws  governing  this  reversible  change 
in  state  are  the  following:  If  the  salts  are  arranged 
according  to  their  precipitating  power,  the  acid  ions  (or 
anions)  always  follow  each  other  in  the  same  order  with 
any  given  metallic  ion,  and,  conversely,  with  any  acid 
ion  the  metallic  ions  (or  cations)  always  follow  each  other 
in  the  same  order.  The  precipitating  power  of  any 
salt  represents,  therefore,  the  product  of  the  effects  of 
its  constituent  ions,  and  the  properties  of  these  ions  are 
to  a  large  extent  independent  of  each  other. 

A  second  law  governs  the  character  of  the  ionic  effects. 
It  was  found  that  the  ions  of  a  salt  antagonize  each  other 
in  bringing  about  changes  in  the  physical  state  of  a  colloid, 
for  the  one  ion  has  a  precipitating  action,  while  the  other 
has  a  solvent  action,  and,  as  the  one  or  the  other  ion  has 
the  upper  hand,  the  salt  under  consideration  either  pre- 
cipitates or  prevents  the  precipitation  of  protein.  The 
effectiveness  of  ions  is  expressed  in  the  following  series: 

Cations  arranged  in  the  order  of  their  precipitating 
power.  The  most  powerful  comes  first:  sodium,  potas- 
sium, ammonium,  magnesium. 

Anions  arranged  in  the  order  in  which  they  prevent 
precipitation.  The  most  powerful  comes  last:  sulphate, 
citrate,  tartrate,  acetate,  chloride,  nitrate,  bromide,  iodide, 
sulpha  cyanate. 

To  render  what  follows  more  intelligible  it  is  necessary 


PHYSICO-CHEMICAL  PROPERTIES.  93 

to  touch  upon  the  relation  of  the  alkaline  earths  to  the 

proteins. 

The  protein  precipitates  produced  through  the  action 
of  the  alkaline  earths  are  irreversible  in  so  far  as  the  solu- 
tion of  a  precipitate  that  has  once  been  produced  is 
difficult  and  scarcely  leads  to  the  restitution  of  an  un- 
changed protein.  The  elTccts  of  calcium,  strontium,  and 
barium  are  determined  to  a  large  extent  through  the 
presence  of  other  ions  simultaneously  present.  Under 
these  circumstances  the  effects  of  the  ions  of  a  salt  of 
an  alkali  metal  also  antagonize  each  other,  only  in  a  way 
opposite  to  that  observed  in  precipitations  produced 
through  pure  neutral  salts.  The  formation  of  a  pre- 
cipitate in  a  solution  of  native  protein  through  the  alkaline 
earths  is  favored  by  anions  and  inhibited  by  cations.  The 
anions  under  these  circumstances  arrange  themselves 
in  the  following  order,  in  which  the  most  powerful  prc- 
cipitants  come  first: 

A  relate,  chloride,  nitrate,  bromide,  iodide,  sulphocyanate. 

The  cations  arrange  themselves  in  the  following  order 
in  which  the  greatest  inhibitor  of  precipitation  is  put 
first : 

Magnesium,  ammonium,  potassium,  sodium. 

Nothing  stands  against  the  assumption  that  it  is  the 
protein  constituents  of  protoplasm  that  constitute  the  point 
of  attack  of  the  ions  in  the  organism,  and  this  belief 
cannot  only  be  supported  by  experiment,  but  is  also  of 
heuristic  value. 

The  two  chief  laws  of  protein  precipitation,  the  additive 
and  the  antagonistic  effects  of  ions,  hold  also  for  the 
physiological  properties  of  ions.  All  cations,  for  example, 
have  certain  physiological  characteristics  in  common,  in 


94  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

that  they  increase  more  or  less  the  irritability  of  nerves 
and  muscles,  excite  intestinal  activity  even  to  the  point 
of  producing  a  gastro-enteritis,  and  usually  increase  blood- 
pressure.  The  solvent  action  upon  protein  and,  running 
parallel  with  it,  the  physiological  effects  of  the  anions 
are  the  more  pronounced  the  further  we  pass  along  the 
series  of  anions  given  above.  The  protein  precipitating 
salts,  such  as  the  sulphates,  citrates,  and  tartrates,  when 
these  are  connected  with  the  overbalancing  properties 
of  the  metallic  ions,  are  all  cathartics.  The  salts  which 
follow  these,  more  especially  the  nitrates,  bromides,  io- 
dides, and  sulphocyanates,  show  the  characteristics  of  the 
anions;  they  are  sedative  in  their  action  and  decrease 
blood-pressure.  The  relationship  between  them  is  in- 
dicated also  in  the  similarity  with  which  they  bring  about 
an  acne  and  coryza.  For  the  sulphocyanates  these 
pharmacological  properties  were  deduced  from  the  group- 
ing given  above  and  verified  on  patients. 

The  experimental  study  of  the  effects  of  sulphocyanates 
has  proved  fruitful  in  yet  another  way,  in  that  the  sulpho- 
cyanate  anions,  representing  as  they  do  the  last  members 
of  the  anion  series,  allow  one  to  study  the  proper- 
ties of  anions  in  a  particularly  pure  form.  Sulpho- 
cyanates can  be  used  first  of  all  in  order  to  ascertain 
more  accurately  the  physiological  relations  between  salts 
and  esters.  Between  the  strongly  ionized  salts  and  the 
scarcely  dissociable  esters  (which  represent  combinations 
between  alcohols  and  acids)  there  exists  a  great  difference 
in  their  power  of  penetrating  a  cell.  While  the  latter, 
according  to  the  extensive  investigations  of  Overton, 
readily  enter  a  cell  because  of  their  solubility  in  its  lipoids, 
— lecithin,  cholesterin,  cerebrin,  etc., — the  salts  enter  the 


PHYSICO-CHEMICAL   PROPERTIES.  95 

protoplasm  only  with  difficulty.  Since,  however,  the 
esters  are  saponified  in  the  organism,  in  consequence  of 
which  the  anions  of  the  acids  become  free,  a  physiological 
ion  effect  might  nevertheless  be  expected  under  favor- 
able conditions,  even  after  the  administration  of  esters. 
Such  an  effect  will  become  apparent,  however,  only  when 
in  a  readily  dissociated  ester  some  anion  is  present  that 
has  characteristic  physiological  properties  and  is  suf- 
ficiently active  physiologically  to  show  itself,  otherwise 
the  narcotic  and  circulatory  effects  common  to  all  esters 
conceal  the  intoxication  picture.  If  for  purposes  of 
comparison  experiments  are  made  with  sodium  sulpho- 
cyanate  and  the  amyl  ester  of  sulphocyanic  acid,  a  typical 
sul pliocyanate  intoxication  occurs  in  both  cases.  Careful 
analysis  shows  that  this  consists  in  a  fall  in  blood-pressure 
brought  about  through  a  decrease  in  the  energy  of  the 
heart  muscle,  a  subsequent  increase  in  pressure  through 
stimulation  of  the  vascular  centres  and  great,  principally 
central,  stimulation  of  the  vagus.  While,  however,  the 
intravenous  injection  of  two  to  three  drops  of  the  ester 
suffice  to  bring  about  a  rapid  and  fatal  intoxication  in 
a  medium-sized  dog,  eight  to  ten  grams  of  sodium  sulpho- 
cyanate  must  be  introduced  intravenously  to  bring  about 
the  same  effect.  This  enormous  difference  in  toxicity 
shows  that  in  the  amyl-sulphocyanate  intoxication  the 
ester  readily  enters  the  cells,  because  of  its  solubility  in 
the  lipoids,  and  that  not  until  it  has  arrived  in  the  cells 
are  its  anions  set  free.  These  same  ions,  when  already 
formed,  enter  the  cells  only  with  difficulty,  in  consequence 
of  which  the  body  must  be  charged  with  a  great  excess 
of  sodium  sulphocyanate  in  order  to  bring  about  the 
same  decree  of  intoxication, 


96  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

Numerous  instances  in  pharmacology,  in  which  any 
alcoholic  radicle  in  an  ester-like  combination  with  an  acid 
is  required  to  bring  about  any  specific  effect,  can,  I  be- 
lieve, be  explained  in  the  same  way.  The  alcohol  radicle 
only  renders  possible  the  ready  absorption  of  the  substance 
by  the  cell;  the  anion  connected  with  it  is  the  really 
active  principle.  Cocaine  is,  for  example,  a  methyl  ester 
of  benzoylecgonin,  a  substituted  tropincarbonic  acid. 
The  benzoylecgonin,  the  real  carrier  of  the  medicinal 
properties,  is  however  twenty  times  less  poisonous  than 
its  ester,  cocaine,  and  does  not  possess  the  anaesthetic 
properties  of  the  latter.  Only  after  being  converted  into 
an  ester,  through  any  alcohol  whatsoever,  is  the  cocaine 
effect  produced.  Existence  in  the  form  of  an  ester  is 
apparently  always  the  sine  qua  non  o]  a  useful  local 
ancesthetic  whose  active  anion  must  enter  the  endings  of 
the  sensory  nerves.  Einhorn  has  found  that  a  large 
number  of  cyclic  and  heterocyclic  esters  are  able  to  bring 
about  a  local  anaesthesia,  and  has  been  able  to  discover 
valuable  substitutes  for  cocaine  in  the  orthoforms,  which 
represent  methyl  esters  of  amido-oxybenzoic  acid,  and  in 
nirvanin,  a  diethylglycocoll  compound  of  orthoform- 
Eucaine  and  anaesthesin  are  also  esters,  the  latter  one 
of  p-amido-benzoic  acid.  Without  being  directly  con- 
cerned in  the  physiological  effect  produced,  the  presence 
of  an  alcohol  radicle  in  the  compound  first  renders  such 
an  effect  possible,  for  only  under  these  circumstances  is 
the  active  acid  ion  present  in  sufficient  concentration  at 
its  point  of  physiological  attack.  Arecaidin,  which 
chemically  represents  a  methyltetrahydronicotinic  acid, 
is  scarcely  active  physiologically,  while  its  methyl  ester, 
arecolin,  represents  the  toxic  principle  of  the  areca-nut, 


PH  YSICi  >■  Q IEMICAL   1 7v  <  )l  'UK  IlliS.  9  7 

The  number  of  these  illustrations  might  easily  be 
multiplied.  In  passing  I  only  wish  to  point  out  that  the 
activity  of  the  metallic  ions  can  be  in<  reased  through 
combination  with  an  alcohol  radicle  in  the  same  way  as 
the  activity  of  the  acid  ions.  It  is  possible  in  this  way 
to  bring  about  in  animals  most  acute  metallic  intoxica- 
tions with  the  cthylic  compounds  of  zinc,  mercury,  and 
lead. 

Besides  this  influence  upon  the  effects  of  ions,  brought 
about  through  combination  with  alcoholic  radicles,  de- 
pendent upon  the  fact  that  protoplasm  is  made  up  of 
lipoidal  and  proteoidal  material,  there  still  exists  another 
way  in  which  the  specific  effects  of  many  ions  can  be 
increased  or  decreased,  namely,  through  combination 
with  other  ions.  As  an  example  of  this  we  may  take 
the  behavior  of  the  alkaline  earths  toward  protein  in  the 
presence  of  neutral  salts  of  the  alkali  metals.  As  a  glance 
at  the  lists  of  ions  given  above  shows,  the  protein  precipi- 
tations brought  about  through  the  alkaline  earths  can 
be  inhibited  through  the  addition  of  ions  of  the  alkali 
metals,  or  hastened  through  the  addition  of  anions,  most 
powerful  of  which  is  the  sulphocyanate  anion.  It  seemed 
possible,  therefore,  that  through  proper  experiments  a 
physiological  antagonism  could  be  discovered  to  cxi>t 
between  monovalent  cations  and  the  alkaline  earths,  as 
vail  as  a  synergistic  increase  in  the  effect  of  anions 
through  the  cations  calcium,  strontium,  and  barium. 
This  suspicion,  prompted  by  analogies  existing  between 
experiments  carried  on  in  vitro  and  certain  phenomena 
observed  in  vivo,  could  be  shown  to  be  correct  by  animal 
experiments. 

If  animals  arc  kept  in  a  half  Intoxicated   state  with 


98  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

sulphocyanate — a  state  which  is  characterized  by  a  strong, 
steady  heart  action  and  stimulation  of  the  vagus  nerve 
and  vascular  centres — it  is  possible  to  bring  about  an 
immediate  standstill  of  the  heart,  not  preceded  by  an  in- 
crease in  blood-pressure,  by  injecting  an  amount  of  a 
barium  salt  which,  under  ordinary  circumstances,  scarcely 
affects  the  heart  at  all,  or,  if  it  does,  only  stimulates  it. 
Such  a  heart-failure  may  under  circumstances  occur 
after  the  injection  of  five  milligrams  of  barium  chloride 
into  a  medium-sized  dog.  Since  this  effect  can  be  ob- 
tained even  in  a  completely  atropinized  heart,  or  after 
the  exclusion  of  the  greater  circulation  and  the  nerve- 
centres,  it  is  probable  that  the  salt  affects  the  heart 
directly.  Just  as  in  test-tube  experiments  with  protein, 
barium,  which  is  characterized  by  a  remarkable  affinity 
for  the  musculature  of  the  heart  and  the  blood-vessels, 
is  able  to  join  such  large  amounts  of  neighboring  sulpho- 
cyanate ions  to  the  heart  muscle  in  such  remarkably 
short  time  that  an  acute,  deadly  sulphocyanate  intoxi- 
cation results.  How  small  amounts  of  sulphocyanate 
suffice  in  order  to  bring  about  a  heart  failure,  if  only  it 
reaches  its  point  of  attack  within  the  cells;  was  indicated 
in  the  experiments  described  above  with  sulphocyanate 
esters.  Calcium  and  strontium  act  in  the  same  way  as 
barium,  only,  because  of  their  lesser  affinity  for  the 
musculature  of  the  heart,  larger  doses  are  required 
(Pauli  and  A.  Frohlich). 

The  physiological  antagonism  between  many  ions  which 
we  supposed  to  exist  from  a  certain  parallelism  between 
the  behavior  of  dead  and  of  living  protein,  and  which  has 
been  proved  to  exist  experimentally,  had  been  previously 
discovered  in  another  way  by  the  well-known  American 


PHYSICO-CHEMICAL  PROPBRtlBS.  99 

physiologist  J.  Loeb,  and  rediscovered  under  the  most 
varied  conditions  by  his  numerous  pupils.  We  can  only 
touch  upon  these  investigations  here.  That  they  har- 
monize with  our  own  findings  and  represent  only  an  ex- 
pression t>f  the  general  principle  common  to  them  all 
is,  however,  readily  discernible.  The  starting-point  of 
Loeb's  investigations  is  the  question  of  the  significance 
of  the  different  ions  of  sea-water  for  the  life  processes  of 
marine  animals.  A  great  similarity  was  found  to  exist 
between  the  effects  of  various  ions  upon  phenomena  of 
development  and  upon  the  activities  of  muscle  and  nerve. 
An  interesting  example  is  furnished  by  the  development 
of  the  eggs  of  Fundulus,  a  small  bony  fish.  These  fish 
are  able  to  develop  not  only  in  sea-water  but  also  in  dis- 
tilled water.  If  immediately  after  fertilization  these  eggs 
are  introduced  into  a  sodium  chloride  solution  of  the 
concentration  of  the  sea-water  they  all  die  in  the  course 
of  a  few  hours  without  developing  any  further.  If, 
however,  a  small  amount  of  calcium,  which  also  represents 
a  constituent  of  the  sea-water,  is  added  to  the  sodium 
chloride  solution,  normal  embryos  are  produced.  A 
pure  sodium  chloride  solution  is  poisonous  also  for  the 
adult  animals,  but  this  toxicity,  too,  is  done  away  with 
upon  the  addition  of  a  little  calcium.  Instructive  also 
are  the  effects  of  ions  on  the  rhythmical  contractions  of 
the  swimming-bell  of  medusae.  After  removal  of  the 
central  nervous  system  in  these  animals  the  bell  still  con- 
tracts rhythmically  in  a  pure  sodium  chloride  solution. 
These  contractions  cease,  however,  as  soon  as  certain 
cations,  such  as  calcium  and  strontium,  arc  added  to  the 
solution,  just  as  they  cease  in  sea-water.  In  a  similar 
way,  the  poisonous  effects  of  pure  sodium  chloride  on 


loo  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

heart  muscle  or  its  stimulating  effects  upon  the  excised 
gastrocnemius  of  the  frog  are  also  done  away  with  through 
the  addition  of  calcium  or  strontium. 

Ralph  S.  Lillie  demonstrated  an  analogous  antag- 
onism between  the  effects  of  cations  on  ciliary  movement. 
MacCallum  showed  in  animal  experiments  that  the 
effect  of  cathartic  sodium  salts,  which  is  to  be  looked 
upon  as  an  expression  of  the  activity  of  the  metallic 
ions,  can  be  inhibited  through  administration  of  calcium. 
Martin  Ho  Fischer  was  able  to  demonstrate  that  a 
glycosuria,  brought  about  through  the  injection  of  sodium 
salts  into  rabbits,  can  be  suppressed  through  calcium, 
and,  according  to  Brown  who  discovered  the  same  fact 
independently,  also  through  strontium. 

That  the  relations  between  anions  are  governed  by 
similar  laws  within  and  without  the  organism  is  apparent 
from  the  investigations  of  Torald  Sollmann.  As  this 
author  was  able  to  show  in  his  studies  on  diuresis,  the 
urinary  excretion  of  chlorine  ions  from  the  body  under 
the  influence  of  other  ions  is  to  a  large  extent  independent 
of  the  amount  of  water  secreted  along  with  them.  The 
per  cent,  of  chlorides  in  the  urine  is  increased  through 
administration  of  nitrates,  iodides,  and  sulphocyanates, 
decreased  through  acetates,  phosphates,  and  sulphates. 
It  is  not  difficult  to  recognize  in  this  grouping  the  order 
in  which  the  anions  act  upon  the  proteins.  The  second 
group  acts  less  powerfully,  the  former  more  powerfully 
than  the  chlorine  ions  in  the  effect  of  the  ions  of  the 
alkali  metals  upon  proteins. 

After  what  has  been  said  it  will  no  doubt  be  admitted 
that  a  considerable  material  is  already  at  hand  which  lends 
further  support  to  the  principle  0}  the  many  analogies 


CHANGES   WROUGHT  IN  PATHOLOGY.  I 01 

between  changes  in  the  physical  state  of  colloids  and  the 
changes  which  go  on  in  living  mailer.  It  would,  however, 
be  unfair  to  expect  such  a  principle  to  hold  quantitatively 
for  every  biological  detail.  It  is  subject  rather  to  the 
various  changes  brought  about  through  differences  in 
living  matter  which  vary  with  different  kinds  of  animals 
and  with  different  kinds  of  organs.  While  calcium, 
strontium,  and  barium  have  an  almost  equal  effect  in 
the  presence  of  sulphocyanates  on  egg  albumin  in  a 
test-tube^  the  synergistic  function  of  the  barium  is  the 
most  apparent  of  the  three  in  a  physiological  experiment 
on  the  heart.  In  a  similar  way  Loeb  and  Herbst 
found  that  individual  differences  exist  between  ions  in 
their  effect  upon  different  marine  animals.  Nevertheless, 
the  general  law  governing  all  these  phenomena  appears 
everywhere,  at  one  time  more,  at  another  time  less  dis- 
tinctly, just  as  in  a  musical  composition  the  theme  is 
heard  at  all  times  by  him  who  has  once  learned  it  among 
the  infinite  number  of  its  variations. 


6.  Changes  Wrought  in    Pathology  through  Advances 
in  Physical  Chemistry.* 

Not  until  it  has  been  found  possible  to  explain  the 
anomalies  in  the  functions  of  the  organism  through 
changes  in  the  form  and  in  the  composition  of  its  constit- 
uents can  pathology  consider  its  task  completed.  Its  held 
of  knowledge  grows  in  three  ways:  through  the  experi- 


*  Wandlungen  in  der  Pathologic  durch  die  Fortschritte  der  all- 
gemeinen  Chemie,  Wien,  1905.  Festival  address  at  tin-  third  annual 
meeting  of  the  K.  k.  Gesellschaft  der  Aerzte  in  Vienna,  March  24,  1905. 


102  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

mental  determination  of  the  degree  and  the  direction  of 
changes  in  function ;  through  a  study  of  the  morphological 
and  through  a  study  of  the  chemical  deviations  from  the 
normal  lying  at  the  basis  of  these  changes  in  function. 
When  one  studies  the  development  and  the  present 
status  of  pathology  one  soon  sees  that  this  science  has 
not  grown  with  the  same  rapidity,  nor  equally  well  in 
all  three  directions.  It  has  developed  most  markedly 
toward  the  morphological  side,  least  of  all  toward  the 
chemical  side.  This  difference  is  still  more  apparent 
when  we  study  more  particularly  the  part  that  the  Vienna 
School  has  played  during  the  past  century  in  the  develop- 
ment of  pathology.  Chemical  methods  have  scarcely 
at  all  been  employed,  except  in  the  last  ten  years,  while 
the  morphological  investigations  carried  on  in  Vienna 
during  this  same  century  have  been  truly  brilliant. 

It  may  not  be  without  interest  to  touch  upon  some 
of  the  reasons  that  have  brought  about  such  a  noticeable 
difference  in  the  pursuit  of  these  two  branches  in  our 
school.  It  was,  of  course,  but  natural  that  the  con- 
ceptions of  the  famous  men  of  the  second  great  period 
of  the  Vienna  School  should  have  determined  for  a 
long  time  to  come  the  course  which  further  development 
in  the  past  century  took.  If  this  development  was  chiefly 
morphological  in  character,  then  this  depended  in  large 
measure  upon  the  state  of  chemistry  in  Austria  at  that 
time.  For  the  education  and  the  first  efforts  of  those 
pioneers  occurred  during  an  epoch  when  chemistry  was 
most  deplorably  represented  in  Austria,  followed  and 
taught  as  it  was,  not  experimentally,  but  speculatively. 
A  classical  document  describes  conditions  as  they  were 
in  those  days.     In  one  of  his  memorable  addresses  Lie  big, 


CHANGES  WROUGHT  IN  PATHOLOGY,  103 

in  1837,  so  frankly  and  mercilessly  criticised  the  condi 
lion  of  chemistry  in  Austria  that  it  stem-,  small  wonder 
that  the  succeeding  generation  of  medical  men,  mightily 
influenced  through  the  labors  of  such  as  Corvisart, 
Laennec,  and  Bretonneau,  dedicated  themselves  chiefly 
to  morphology,  which  promised  so  much.  The  experi- 
ences of  medicine  with  a  chemistry  which  had  been  in  the 
main  of  a  speculative  character  no  doubt  also  contributed 
to  this  end.  The  birth  of  iatro-chemistry,  which  through 
Paracelsus,  Helmont,  and  Sylvius  ruled  medicine  in 
the  seventeenth  century,  met  a  just  and  fruitful  opposition 
through  the  morphological  workers.  Later  Boerhave, 
with  whose  entry  the  first  brilliant  epoch  in  medicine  is 
intimately  connected,  most  emphatically  emphasized  the 
great  importance  of  chemical  research  in  pathology,  but 
because  of  its  insufficient  development  chemistry  could 
offer  too  little  at  that  time  to  fulfil  his  promises. 

Not  until  the  wonderful  development  of  organic  and 
applied  chemistry  as  introduced  in  the  middle  of  the 
last  century,  more  especially  by  Liebig,  did  new  paths 
open  up  before  pathology.  In  the  meantime,  however, 
the  morphological  tendency  in  Vienna  had,  under  the 
tremendous  influence  of  its  illustrious  exponents,  obtained 
the  upper  hand,  a  fact  which  helped  to  determine  also 
the  nature  of  the  increase  in  the  faculty.  Into  the  circle 
of  their  influence  were  drawn  the  majority  of  the  younger 
men  of  talent  and  permanently  kept  there.  For  it  resides 
in  the  nature  of  morphological  research  that  it  is  admirably 
adapted  for  the  introduction  of  the  beginner  to  science,  in 
that  it  offers  a  large  number  of  simple  problems  which 
mav  be  solved  without  drawing  upon  a  larger  number  of 
accessory  sciences,  while  its  results,  which  usually  rcpre- 


164  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

sent  a  truthful  description  of  what  has  been  seen,  give 
a  feeling  of  great  security. 

The  far-reaching  results  of  chemical  research  in  the 
last  decade  have  brought  to  us  also  a  gradual  increase 
in  the  general  interest  taken  in  the  chemical  aspects  of 
pathology,  and  so  it  has  been  no  accident  that  this  altered 
point  of  view  has  found  an  expression  in  the  change  in 
the  character  of  the  annual  addresses  made  before  our 
society.  Three  years  ago  we  enjoyed  an  inspiring  pres- 
entation of  the  pathology  of  metabolism,  and  last  year 
brought  us  a  sharply  defined  discussion  of  the  protein 
question,  such  as  only  ripe  experience,  hand  in  hand 
with  critical  judgment,  can  produce.  If  I  to-day  find 
myself  once  more  face  to  face  with  the  problem  of  bring- 
ing before  you  in  our  annual  meeting  another  chapter 
from  the  realm  of  chemistry  as  applied  to  medicine,  I 
must  attribute  this  honor  first  of  all  to  that  great 
new  interest  taken  in  this  subject.  This  subject  is,  in 
fact,  worthy  of  your  greatest  attention,  for  we  stand  at 
present  in  the  midst  of  an  undreamed-of  improvement 
and  development  in  our  point  of  view  in  physiology  and 
pathology,  and  this  strange  and  sudden  change  is  based 
in  particular  upon  advances  in  general  or  physical  chem- 
istry. This  science  has  acquainted  us  with  a  series  of 
fundamental  laws  that  govern  chemical  reactions,  whose 
validity,  influenced  more  or  less  through  special  circum- 
stances, extends  also  to  the  changes  that  go  on  in  living 
organisms. 

It  was  probably  the  first  important  step  for  the  physico- 
chemical  characterization  of  living  matter  when  Graham 
divided  all  bodies  into  colloids  and  crystalloids,  according 


CHANGES   WROUGHT  IN  PATHOLOGY.  105 

to  the  behavior  of  certain  typical  substances.  For  from 
this  division  there  lias  arisen  the  conception  that  all 
living  matter  is  of  necessity  connected  with  the  existent  e 
of  a  colloidal  ground-substance  in  which  all  changes 
take  place.  Nevertheless,  more  than  twenty  years  were 
necessary  before  a  systematic  attempt  was  mack-  to  obtain 
a  conception  of  the  changes  that  go  on  in  living  matter 
from  a  study  of  changes  in  the  state  of  colloids.  In  the 
three  years  from  1888  to  1891  HOFMEISTER  took  the  first 
step  in  this  direction,  in  that,  in  attempting  to  explain 
the  physiological  effects  of  salts,  he  compared  the  effect  of 
salts  upon  colloids  in  a  test-tube  with  the  effect  of  these 
salts  upon  the  animal  organism.  During  the  last  decade 
similar  investigations  have  been  carried  on  with  the 
means  offered  by  physical  chemistry,  which  has  during 
that  time  enjoyed  most  rapid  growth,  and  have,  in  con- 
junction with  the  investigations  of  chemists  on  inorganic 
colloids,  furnished  so  abundant  a  material  that  the  time 
for  a  broad  alliance  between  biology  and  colloidal  chem- 
istry seems  to  have  come.  From  this  most  promising 
section  of  applied  chemistry  I  would  to-day  like  to  take 
a  few  facts  which  to  all  appearances  seem  to  be  of  funda- 
mental biological  importance. 

The  colloidal  substances  are  present  in  two  forms  in 
the  body — in  a  more  or  less  jelly-like  condition  in  the 
cells,  and  in  a  fluid  condition  in  the  blood  and  the  tissue 
juices.  The  laws  of  colloid  chemistry  govern  the  changes 
that  go  on  in  the  cells,  only  these  laws  are  modified 
through  the  metabolism  of  living  matter,  the  character- 
istics of  which  we  do  not  as  yet  understand.  The  behavior 
of  the  extracellular  material  is,  however,  of  a  much 
simpler  character.     In  the  former  case  there  exists  only 


lo6  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

a  certain  parallelism  between  changes  in  colloids  and 
many  manifestations  of  cell  life;  in  the  second,  however, 
we  are  dealing  with  a  direct  applicability  of  the  laws  of 
colloid  chemistry,  controllable  at  any  time  by  experiment. 
We  will  to-day  discuss  only  these  last-named  phenomena, 
the  importance  of  which  has  recently  been  pushed  into 
the  scientific  foreground,  more  especially  through  the 
modern  development  of  the  teachings  of  immunity. 

Before  attempting  an  explanation  of  the  significance 
of  the  phenomena  which  interest  us  especially,  it  is 
necessary  to  obtain  a  clear  conception  of  the  characteristic 
properties  of  the  colloidal  condition.  These  character- 
istics are  best  illustrated  by  the  properties  of  the  colloidal 
solutions  of  metals,  from  which  a  gradual  transition  to 
the  biologically  important  colloids  occurs. 

If  a  clean  metal  plate,  such  as  platinum,  is  put  into 
water  it  assumes  a  weak  electric — in  this  case  negative — 
charge,  while  the  fluid  surrounding  it  becomes  electro- 
positive. According  to  the  fruitful  conceptions  which 
Nernst  has  developed  of  the  source  of  galvanic  currents, 
we  have  to  deal  with  the  following  process :  Just  as  after 
the  solution  of  a  salt — such  as  sodium  chloride — in 
water  the  metallic  portion  is  present  in  the  form  of 
electropositive  particles,  the  acid  portion  in  the  form  of 
electronegative  particles  or  ions,  a  metal  when  dropped 
into  water  also  goes  into  solution  in  traces  to  form 
electropositive  metallic  ions,  while  the  metal  itself  be- 
comes a  negative  electrode.  A  proper  combination  of 
such  metals  having  different  solution  tensions  then  con- 
stitutes a  galvanic  element.  If  now  we  imagine  such 
a  metal  divided  under  water  into  smaller  and  smaller 
particles  until  this  metallic  dust  is  able  by  virtue  of  its 


CHANGES   WROUGHT  IN  PATHOLOGY.  107 

minuteness  to  remain  suspended  in  the  liquid  an  in- 
definite length  of  time,  then  we  have  a  colloidal  solution 
before  US.  Such  a  solution  is  perfectly  clear  and  passes 
unchanged  through  the  finest  filter.  We  can  deduce 
from  the  manner  of  its  origin  its  characteristic  properties 
— such  a  solution  represents  a  suspension  of  fine  elec- 
trically charged  particles,  in  other  •words  minute  elec- 
trodes. If  two  gold  electrodes  connected  with  a  strong 
electric  current  are  introduced,  according  to  the  direc- 
tions given  by  Bredig,  into  pure  water  cooled  by  ice  and 
then  are  carefully  separated  until  a  tiny  arc  appears, 
purplish-red  clouds  begin  to  emanate  from  the  negative 
electrode  as  this  goes  into  solution  in  the  form  of  fine 
dust  particles,  and  the  result  is  the  production  of  the 
beautiful  colloidal  gold  solution  which  Zsigmondy  pre- 
pared previously  by  chemical  means  through  careful 
reduction  of  a  gold  chloride  solution.  Partially  through 
use  of  the  chemical  method,  partially  through  use  of 
the  electrical  method,  a  large  number  of  inorganic 
colloids  have  been  produced,  which  have,  since  Gra- 
ham's fundamental  work,  formed  a  much-cherished  ob- 
ject of  investigation.  But  not  until  recently  has  it 
been  possible  to  deduce  in  a  satisfactory  way  the  laws 
governing  their  varied  behavior  from  variations  in  a 
few  characteristics.  By  utilizing  the  fundamental  work 
of  such  investigators  as  Linder,  Picton,  Hardy,  and 
Bredig,  and  many  of  his  own  experiments,  J.  Billitzer, 
a  Vienna  chemist,  has  been  able  to  show  that  the  chief 
laws  governing  and  the  differences  existing  between  col- 
loids can  all  be  explained  by  variations  in  only  three 
values,  namely,  the  number,  size,  and  electrical  charge 
of    the    suspended    particles.     This    conception,    which 


lo8  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

allows  not  only  a  survey  of  what  has  been  accomplished, 
but  also  allows  us  to  state  in  advance  what  may  be  ex- 
pected to  happen  in  colloidal  solutions,  has,  moreover, 
the  advantage  that  its  suppositions  are  capable  of  being 
tested  experimentally — in  fact,  have  already  been  tested 
in  many  cases. 

We  have  optical  means  at  our  disposal,  for  example, 
by  which  we  can  determine  the  number  and  the  size  of 
the  colloidal  particles.  If  a  colloidal  solution  is  placed 
in  a  bundle  of  intense  light  rays,  the  fine  particles  of  the 
solution  reflect  the  light  in  part,  as  can  be  determined 
through  its  polarization.  The  absorption  of  different 
portions  of  the  spectrum  may  also  give  a  clue  regarding 
the  size  of  the  particles.  Finally,  Siedentopf  and 
Zsigmondy  have  made  it  possible  with  their  ingenious 
ultramicroscope  to  determine  the  number  and  size  of  the 
colloidal  particles.  The  electrical  condition  of  the  sus- 
pended particles  we  can  recognize  from  their  behavior 
in  the  electric  current,  in  that  they  migrate,  according  to 
their  electrical  charge,  either  toward  the  positive  pole 
when  they  are  negatively  charged,  or  toward  the  negative 
pole  when  they  are  positively  charged. 

These  facts  allow  us  to  understand  a  process  which 
has  long  served  as  the  prototype  of  most  of  the  colloid 
reactions  and  which  explains  many  important  questions 
in  physiology  and  pathology,  namely,  the  precipitation  of 
colloids. 

It  has  already  been  pointed  out  that  the  salts,  acids, 
and  bases  dissociate  in  part  in  aqueous  solution  into 
their  oppositely  charged  constituents,  the  ions.  Let  us 
suppose  now  that  a  sufficient  number  of  such  ions  are 
introduced  into  a  colloidal  solution  of  a  metal  which 


CHANGES   WROUGHT  IN  PATHOLOGY.  109 

represents  a  suspension  of  weakly  charged  el«  tronegative 
particles.  In  consequence  of  electrical  attraction,  the 
negative  colloidal  particles  will  colled  about  the  electro- 
positive ions,  until  through  the  heaping  up  of  a  suffi- 
cient Dumber  of  such  particles  the  collecting  ion  will 
lie  electrically  neutralized.  When  the  aggregates  thus 
formed  have  reached  a  sufficient  si/A',  the  solution 
becomes  turbid,  and  finally  a  precipitate  drops  to  the 
bottom. 

We  arc  able  to  foretell  the  possibilities  which  resull 
from  a  change  in  the  number,  size,  and  electrical  charge 
of  the  particles  of  a  colloid,  all  of  which  can  be  proved  by 
experiment.  When  the  number  of  particles  is  decreased, 
the  probability  that  a  sufficient  number  will  be  collected 
together  through  added  ions  for  the  formation  of  large 
aggregates  is  also  decreased,  and  finally  a  stage  is 
reached  in  the  concentration  of  the  colloid  below  which 
precipitation  does  not  occur.  The  precipitation  is  also 
rendered  difficult  when  the  particles  are  very  small  and 
carry  but  a  weak  charge,  because  under  these  circum- 
stances too  large  a  number  of  the  particles  have  to  be 
collected  together.  If,  on  the  other  hand,  the  electrical 
charge  of  the  particles  is  too  great,  then  too  few  suffice 
to  neutralize  the  oppositely  charged  ions,  and  the  aggre- 
gates formed  arc  too  small  to  settle  to  the  bottom.  A 
medium  charge,  a  sufficient  number,  and  a  sufficiently 
large  size  of  the  colloidal  particles  constitute,  therefore, 
the  optimum  for  precipitation.  Just  as  we  have  electro- 
negative metallic  colloids,  we  have  also  electropositive 
colloids.  Oppositely  charged  colloids  precipitate  each 
other  in  the  same  way  as  the  ions  of  salts  precipitate  a 
colloid,  only  in  consequence  of  the  size  of  the  reacting 


no  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

particles  the  conditions  for  the  formation  of  large  aggre- 
gates are  especially  favorable. 

We  have  yet  to  speak  of  a  few  typical  observations  on 
the  precipitation  of  colloids  that  have  become  of  great 
importance  for  certain  questions  in  biology.  Such,  for 
example,  is  the  often-observed  variability  in  colloids.  This 
variability  often  does  not  attain  a  stabile  end  state  until 
after  a  very  long  time.  It  has  been  found  that  this  origi- 
nal instability  is  dependent  chiefly  upon  the  presence  of 
impurities  introduced  during  the  preparation  of  the 
colloid,  which  because  of  their  slight  amount  do  not 
make  themselves  felt  until  a  long  time  has  passed.  As 
soon  as  this  slow  process  of  neutralization  has  come  to 
an  end,  the  colloid  is  in  a  stabile  condition. 

A  further  very  important  observation  is  the  great 
influence  that  time  has  upon  the  formation  of  a  precipitate. 
We  usually  require  very  different  amounts  of  a  precipi- 
tating salt  or  a  colloid,  depending  upon  whether  the 
precipitate  is  to  be  brought  down  at  once  or  more  slowly. 
Not  rarely  the  amount  of  precipitating  substance  used 
in  the  second  case  is  larger  than  in  the  former.  This 
is  dependent  upon  the  following  fact:  If  the  precipitating 
colloid  A  is  at  once  added  to  the  colloid  B,  the  particles 
are  present  everywhere  in  the  mixture  in  the  size  and 
with  the  electrical  charge  which  they  possess  in  the 
unmixed  individual  colloids  A  and  B.  Things  are 
different,  however,  when  small  portions  of  B  are  added 
one  after  the  other  to  A.  Under  these  circumstances,  if 
the  reaction  does  not  take  place  too  rapidly,  new  aggre- 
gates of  B  and  A  are  formed  upon  the  addition  of  the 
first  amount  of  colloid,  which  are  not  entirely  neutral 
and  which  differ  in  size  and  charge  from  the  original 


CHANGES   WROUGHT  IN  PATHOLOGY.  Ill 

particles  of  .1.     Every  new  addition  of  B  will  encounter 

new  conditions  in  this  regard,  and,  as  experience  has 
taught,  usually  conditions  less  favorable  so  far  as  pre- 
cipitation is  concerned.  The  result  is  that  under  these 
conditions  of  partial  saturation  more  precipitating  ma- 
terial is  used  up  than  when  all  is  added  at  once,  and 
that  a  series  of  intermediate  bodies  between  the  pure 
substances  A  and  B  and  the  fully  neutralized  mixture 
AB  are  formed.  These  intermediate  bodies  are  built 
according  to  the  type  xAyB,  in  which  x  and  y  vary 
within  certain  limits. 

A  third  possibility  that  interests  us  is  the  following. 
The  aggregates  formed  through  neutralization  of  the  par- 
ticles of  two  oppositely  charged  colloids  are  often  held 
loosely  together  through  slight  electric  forces.  If  an 
excess  of  one  or  the  other  colloid  is  added  to  such  a 
precipitate,  the  new  particles  will,  because  of  their  elec- 
trical charge,  enter  into  competition  with  the  attraction 
forces  existing  in  the  neutral  aggregates,  and  by  diminishing 
their  size  and  electrifying  the  particles  cause  the  pre- 
cipitate to  go  back  into  solution.  As  soon  as  a  certain 
quantitative  relation  exists  between  the  two  colloids,  the 
precipitate  will  therefore  attain  a  maximum  and  will  go 
back  into  solution  as  soon  as  one  or  the  other  colloid 
is  present  in  excess.  This  is  a  familiar  and  well-studied 
relation  existing  between  colloids. 

The  experimental  facts  that  have  just  been  recited 
•were  arranged  so  as  to  be  ready  for  immediate  application 
to  one  of  the  most  important  and  interesting  chapters 
of  medicine,  the  immunity  reactions.  We  shall  deal 
more  particularly  with  that  difficult  and  much-argued 
relation  between  toxin  and  antitoxin.     On  thiss  ubject 


112  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

there  exist  a  large  number  of  valuable  quantitative 
investigations,  of  which  must  be  mentioned  in  particular 
the  fundamental  work  of  Ehrlich  on  diphtheria  toxin. 

I  may  perhaps  be  allowed,  before  entering  into  details, 
to  touch  upon  those  few  leading  points  which  render 
possible  a  simpler  and  more  satisfactory  conception  of 
the  relation  of  toxin  to  antitoxin  than  has  until  now 
been  possible.  Two  assumptions  suffice,  both  of  which 
rest  upon  a  fully  established  experimental  basis  and  are 
generally  accepted  without  contradiction:  the  colloidal 
constitution  of  toxins  and  antitoxins,  and  their  ability 
to  neutralize  each  other.  Through  these  suppositions 
is  rendered  possible  the  extension  to  the  dark  relations 
existing  between  toxin  and  antitoxin  of  our  advanced 
insight  into  the  process  of  colloidal  precipitation.  As  an 
actual  matter  of  fact,  we  are  dealing  in  both  cases  with  a 
neutralization  of  colloids,  only  the  criterion  which  exists  to 
show  that  such  a  neutralization  has  occurred  is  different  in 
the  two  cases.  For  in  the  first  case  this  consists  in  the 
production  of  macroscopically  visible  aggregates,  in  the 
second  in  the  formation  of  non-poisonous  ones.  The 
similarity  between  the  general  laws  governing  the  two 
sets  of  phenomena  is,  in  truth,  striking. 

It  is  a  well-known  fact,  for  example,  that  especially  diph- 
theria toxin  when  kept  for  longer  periods  of  time  under- 
goes changes  which  are  attributed  to  the  formation  of 
various  complexes  from  the  originally  simple  toxin.  An 
analogous  phenomenon  is  counted  among  the  first-observed 
and  best-known  facts  of  colloids  in  general.  It  is  de- 
pendent upon  the  presence  of  neutralizing  impurities 
which  are  in  the  course  of  time  able  to  render  manifest 
their  effect  in  the  production  of  aggregates.     The  more 


CHANGES    WROUGHT  IN  PATHOLOGY.  113 

concentrated  a  colloidal  solution,  the  richer  it  is,  other 
things  being  equal,  in  impurities,  and  the  less  stabile  in 
consequence.      In   the   course   of    time   the    proa 

neutralization  in  the  colloidal  solution  comes  to  an 
vm\,  alter  which  it  remains  stabile.  Ehrlich  has 
been  able  to  observe  similar  faets  in  the  case  of 
diphtheria  toxin  which  is  kept  a  sufficiently  long  time. 
And  we  know  from  the  observations  of  Paltauf  on 
the  loss  in  strength  of  stored  immune  sera,  and  a  recent 
excellent  Investigation  of  Pick  and  Schwoner,  that  in 
antitoxin,  especially  in  the  case  of  the  high-potency 
sera,  the  tendency  to  form  aggregates  is  very  great.  That 
this  tendency  toward  the  formation  of  aggregates  must 
be  subject  to  the  greatest  variations  under  our  present 
system  of  obtaining  the  impure  toxin  and  antitoxin 
solutions  is  readily  intelligible.  In  the  preparation  of 
inorganic  colloids  we  have  also  only  lately  and  by  no 
means  in  all  cases  succeeded  in  obtaining  stabile  and 
uniform  solutions,  through  perfection  of  technic  and 
ideal  cleanliness  of  material. 

Upon  the  variations  in  the  original  properties  of  colloids 
arc  also  dependent  the  variations  in  the  colloidal  mix- 
tures. This  explains  that  variability  which  has  been 
observed  in  the  behavior  of  toxin-antitoxin  mixtures 
and  which  originally  wrought  great  confusion  in  this 
question.  We  have  already  touched  upon  the  great 
differences  shown  in  the  behavior  of  colloidal  mixtures, 
depending  upon  whether  they  are  precipitated  at  once 
or  in  fractions.  It  is  of  value  to  enter  a  little  into  the 
details  of  the  relations  existing  when  toxin  and  antitoxin 
aiv  mixed  together,  for  the  observations  of  Ehrlich 
on    the    fractional    saturation    of    toxin    constitute    the 


H4  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

foundation  of  our  modern  conceptions  of  its  nature.  If 
we  add  to  a  certain  amount  of  a  colloid  A  a  much  smaller 
amount  of  a  neutralizing  colloid  B,  then,  generally 
speaking,*  a  part  of  A  is  not  completely  neutralized,  while 
the  remaining  part  remains  free,  but  B  is  distributed 
over  and  combines  with  as  large  a  number  of  the  colloidal 
particles  of  A  as  is  possible.  As  a  result,  new,  incom- 
pletely neutralized  aggregates  are  formed.  By  this  means 
the  number,  size,  and  electrical  condition  of  the  particles 
become  changed,  and  it  depends  entirely  upon  the  char- 
acter of  these  new  values  whether  the  tendency  toward 
a  formation  of  further  aggregates  upon  the  addition  of 
a  second  portion  of  B  is  favored  or  inhibited.  When 
such  a  second  addition  is  made,  new  aggregates  with 
new  properties  are  again  produced.  If  we  have  deter- 
mined the  amount  of  antitoxin  necessary  to  just  neu- 
tralize a  lethal  dose  of  toxin,  we  will  need  n  times  this 
amount  to  neutralize  an  #-times  dose  of  toxin.  Things 
are  different,  however,  as  soon  as  we  try  to  saturate 
gradually,  through  the  addition  of  succeeding  small 
amounts  of  antitoxin,  an  n  dose  of  toxin,  as  Ehrlich 
has  done.     Under  these  circumstances  we  can  get  only 

*  It  cannot  be  discussed  in  this  paper  in  how  far  neutralization 
velocity  and  reversibility  of  the  formation  of  aggregates  determine  the 
character  of  the  course  of  the  reaction.  The  more  important  instances 
can,  however,  be  reviewed.  Reversibility  is  always  only  partial,  and 
decreases  steadily  from  the  moment  of  neutralization.  Even  such 
stabile  colloidal  changes  as  the  coagulation  of  egg  albumin  through 
heat  or  concentrated  mineral  acids  are  reversible  at  the  moment  that 
they  are  brought  about.  In  the  precipitation  of  protein  through  phenol, 
alcohol,  or  neutral  salts  the  effect  of  time  and  the  degree  of  reversibility 
increase  from  the  first  toward  the  last.  This  general  property  of 
colloids  has  in  recent  discussions  of  immunity  assumed  an  important 
part  under  the  beading  of  secondary  fixation  of  toxin-antitoxin. 


CHANGES    WROUGHT  IN   PATHOLOGY.  115 

those  transitional  toxin  antitoxin  compounds  which  show 
great  variations  in  their  reactions.  This  phenomenon 
lias   been    responsible    for    the   development   of    a    rich 

nomenclature.  All  the  relations  between  toxin  and 
antitoxin  are  much  complicated  by  the  fact  that  diph- 
theria toxin,  as  has  already  hern  pointed  out,  may  from 
the  start  enter  into  a  reaction  with  antitoxin,  with  aggre- 
gates which  arc  by  no  means  all  alike.  To  this  is  still 
to  be  added  the  following  fundamental  peculiarity  in  the 
reactions  of  the  toxin.  The  toxicity  of  diphtheria  toxin 
and  its  relations  to  antitoxin  arc  able  to  vary  independ- 
ently of  each  other,  a  behavior  which  finds  expression,  for 
example,  in  the  fact  that  a  toxin  requires  approximately 
thesame  amount  of  antitoxin  for  neutralization  no  mat- 
ter whether  its  toxicity  is  high  or  diminished  through  age. 
This  phenomenon,  which  represents  another  of  Ehrlich's 
discoveries,  was  explained  by  assuming  that  the  toxin 
is  composed  of  a  haptophore,  or  binding  group,  and  a 
toxophore,  or  poison-bearing  group.  We  must  not  fail 
to  consider,  however,  that  we  are  dealing  with  a  reaction 
of  the  colloidal  toxin  with  two  different  kinds  of  colloids 
— with  the  antitoxin  and  with  the  constituents  of  the 
cell. 

Slight  changes  in  the  colloidal  properties  of  a  body 
are,  however,  able  to  affect  one  part  of  its  reactions  and 
leave  another  part  free.  An  interesting  example  of  this 
is  furnished  by  the  behavior  of  colloidal  gold  toward 
mercury,  which  I  introduce  because  we  are  dealing  under 
these  circumstances  with  reactions  between  elements, 
reactions  which  no  one  will  be  inclined  to  attribute  to 
properties  of  special  atomic  groups.  Colloidal  gold 
shows  the  properties  of  the  pure  metal,   except   that  it 


n6  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

does  not  form  an  amalgam  with  mercury.  A  similar 
behavior  can  be  mimicked  in  immunity  reactions  when 
the  haptophore  groups  are  lost  while  the  ergophore 
groups  are  retained,  or  conversely.  According  to  Bil- 
litzer's  observations,  it  is  the  fact  that  both  metals 
possess  the  same  electrical  charge  which  prevents  the 
formation  of  an  amalgam.  How  easily,  however,  it  may 
be  concluded  from  work  with  colloidal  mixtures  that 
new  chemical  compounds  have  been  produced  is  indicated 
by  the  interesting  fact  that  no  less  a  man  than  Berzelius 
did  this  in  a  study  of  colloidal  gold  and  came  to  similar 
conclusions,  as  did  Ehrlich  in  a  study  of  toxin-anti- 
toxin mixtures.  In  gold-purple,  which  has  been  recog- 
nized through  an  excellent  investigation  of  Zsigmondy 
as  a  mixture  of  colloidal  gold  and  colloidal  stannic  acid, 
the  gold  shows  some  variations  in  reaction.  Misled 
by  this  fact,  Berzelius  drew  the  conclusion  that  gold 
exists  in  gold-purple  as  the  oxide.  It  is  a  fact  of  great 
importance  that,  in  a  mixture  of  two  colloids  A  and  B, 
the  properties  of  A  disappear  for  many  reactions,  while  for 
others  those  of  B  disappear.  According  to  the  beautiful 
experiments  of  Zsigmondy,  in  a  mixture  of  orthostannic 
and  metastannic  acids  certain  of  the  chemical  properties 
of  the  metastannic  acid  are  concealed  by  the  ortho-com- 
pound, while  toward  other  reagents  the  properties  of  the 
ortho-compounds  fall  entirely  into  the  background.  Every 
species  of  animal  represents  a  different  reagent  toward 
the  same  mixture  of  toxin  and  antitoxin,  in  which  at  one 
time  the  effect  of  the  toxine,  at  another  that  of  the  anti- 
toxin, may  hold  the  upper  hand.  Besides  the  phenom- 
ena of  neutralization,  this  fact  has  done  most  to  sup- 
port the  belief  in  the  existence  of  toxins  having  different 


CHANGES   WROUGHT  IN  PATHOLOGY.  i>7 

chemical  compositions.    We  are  able  to  recognize  in  this 
onlv  a  general  property  of  colloidal  mixtures,  the  laws 

governing  which  ZsiGMONDY  has  formulated  in  his  inves- 
tigations on  CASSIUS'S  gold-purple  in  the  following  way: 

'•  As  most  important  I  consider  the  recognition  of  the 
fact  that  a  mixture  of  colloid^  may,  under  certain  circum- 
stances, behave  as  a  chemical  compound,  and  that  the 
properties  of  one  of  the  constituents  of  such  a  mixture 
may  be  concealed  through  those  of  another. " 

An  especially  remarkable  illustration  of  the  identity 
of  the  neutralization  of  toxin  with  antitoxin  and  the 
neutralization  of  two  colloids  is  furnished  by  a  phenomenon 
which  has  also  been  discovered  by  Ehrlich,  and  a  de- 
scription of  which  we  will  introduce,  with  a  few  figures. 

A-  the  standard  of  a  lethal  dose  of  diphtheria  toxin 
is  taken  the  amount  which  will  kill  a  guinea-pig  of  250 
grams  in  from  four  to  five  days.  Ehrlich  added  to  one 
immunitv  unit — that  is,  one  cubic  centimeter  of  antitoxin 
serum,  capable  of  counteracting  the  poisonous  effects  of 
100  simple  lethal  doses — enough  diphtheria  toxin  until 
the  mixture  showed  no  toxic  properties  and  indicated 
the  amount  of  toxin  necessary  to  accomplish  this  by 
L0.  This  is  usually  less  than  one  hundred,  for  the  neu- 
tralizing toxin  has,  as  a  rule,  stronger  neutralizing  than 
toxic  properties.  Without  a  knowledge  of  the  properties 
of  colloids  one  would  expect  that  through  the  addition  of 
a  simple  toxic  dose  to  the  approximately  neutralized  mix- 
ture L0  one  would  obtain  a  product  capable  of  killing 
a  normal  guinea-pig  in  from  four  to  five  days.  Ehrlich 
found,  however,  that  several  simple  toxic  doses  have  to 
be  added  before  the  mixture  again  assumes  tin'  effect  of 
a  free  lethal  dose.     From  our  knowledge  of  the  formation 


Il8  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

of  aggregates  in  the  process  of  colloidal  precipitation,  this 
result  was  to  be  expected,  for  each  of  the  toxin  doses 
added  to  L0  distributes  itself  over  all  the  aggregates  already- 
present,  in  consequence  of  which  the  mixture  can  attain 
the  unit  toxicity  only  after  several  doses  have  been  added 
to  it. 

Through  an  investigation  carried  out  by  the  chemist 
Biltz,  who  has  brought  much  light  into  this  field,  we 
are  familiar  with  phenomena  observed  upon  inorganic 
colloids  that  are  entirely  analogous  to  the  Ehrlich 
phenomena  just  described.  Biltz  studied  quantitatively 
the  neutralization  of  arsenious  acid  by  its  well-known 
antidote,  iron  hydroxide,  of  which  the  former  represents 
an  electronegative  radicle,  the  latter  an  electropositive 
colloid.  These  investigations  showed  that  a  neutralized 
mixture  of  the  two — that  is,  one  corresponding  with  the  L0 
toxin-antitoxin  mixture,  therefore — still  has  the  power  of 
uniting  with  arsenious  acid  and  rendering  several  poison- 
ous single  doses  harmless.  A  certain  analogue  of  the 
Ehrlich  phenomenon  in  the  field  of  precipitation  is  per- 
haps to  be  found  in  the  following.  It  is  often  possible,  as 
has  already  been  pointed  out,  to  dissolve  a  precipitated 
colloid  in  an  excess  of  the  precipitating  colloid.  If  the 
addition  of  a  colloidal  solution  to  a  neutralized  precipitated 
mixture  corresponding  with  the  Lo  value  of  Ehrlich  is 
continued  until  the  precipitate  is  redissolved,  much  more 
of  this  colloid  is  required  for  this  purpose  than  when  a 
colloid  has  added  to  it  all  at  once  an  excess  of  a  second 
colloid.  The  intimate  connection  between  this  phenom- 
enon and  the  behavior  of  a  colloid  when  precipitated 
through  the  addition  of  successive  small  doses  of  a  second 
colloid  can  readily  be  seen.     The  procedure  is  the  same, 


CHANGES   WROUGHT  IN  r/ITHOLOGY.  1 19 

only  it  is  executed  in  different  time  and  follows  a  different 
scale. 

Wc  still  have  to  consider  a  few  possibilities  which  can 
be  deduced  from  the  properties  of  differently  charged 
colloids  and  which  are  realized  in  the  phenomena  of 
precipitation  and  in  the  phenomena  of  neutralizing  a 
toxin.  One  of  these  is  the  antagonistic  effects  that 
small  and  large  amounts  of  one  colloid  may  have  upon 
a  second.  Number,  size,  and  charge  of  the  particles 
of  a  colloid  need  not  at  all  be  related  to  each  other  in 
such  a  way  as  to  best  favor  neutralization.  For  this 
reason  different  colloids  are  not  precipitated  with  the  same 
ease.  Under  certain  circumstances  a  decrease  in  the 
electrical  charge  with  a  slight  change  in  the  size  of  the 
particles  may  make  a  colloid  more  stabile.  This  may 
be  brought  about  through  the  addition  of  the  right 
amount  of  a  neutralizing  colloid.  Gelatine  in  small 
amounts  may,  for  example,  protect  another  colloid  against 
a  precipitation  which  at  a  greater  concentration  it  itself 
brings  about.  A  striking  example,  which  until  now  has 
been  regarded  only  as  a  curiosity,  of  such  an  antagonistic 
effect  of  one  and  the  same  colloid  has  been  studied  by 
Jacoby,  who  found  that  the  toxicity  of  crotin  is  increased 
through  the  addition  of  small  amounts  of  antitoxin,  while 
it  is  decreased  and  neutralized  through  the  addition  of 
larger  amounts. 

A  well- recognized  conclusion  to  be  drawn  from  the 
behavior  of  colloids  toward  each  other  is  the  following: 
It  is  by  no  means  immaterial  whether  a  colloid  A  has 
small  amounts  of  a  colloid  B  added  to  it,  or  whether  B 
has  small  amounts  of  A  added  to  it,  and  the  aggregates 
formed  in  the  two  cases  will,   in  general,  be  different 


120  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

from  each  other.  If  we  begin  with  an  excess  of  toxin 
to  which  successive  small  amounts  of  antitoxin  are  added, 
the  formation  of  aggregates  will  be  able  to  follow  a 
different  course  than  when  the  reverse  is  the  case,  when 
we  start  with  an  excess  of  antitoxin.-  Ehrlich  has 
worked  according  to  the  first  method,  while  Pick  and 
Schwoner  utilized  the  second  method  and  came  to  the 
conclusion  that  the  laws  governing  the  combination 
between  toxin  and  antitoxin  were  totally  different  from 
those  discovered  by  Ehrlich.*  It  can  easily  be  seen 
how  through  changes  in  only  a  few  conditions  an  enormous 
variety  in  the  character  of  the  colloidal  reactions  is 
brought  about,  a  behavior  which  is  rendered  apparent 
through  a  consideration  of  the  numerous  well-studied 
transitions  existing  between  colloids  and  crystalloids. 
A  colloidal  solution  consists  of  a  suspension  of  fine  par- 
ticles which  have  assumed  an  electrical  charge  through 
giving  off  ions,  just  as  have  electrodes.  If  now  the 
suspended  particles  become  steadily  smaller,  while  at  the 
same  time  their  electrical  charge  grows,  they  approximate 
more  and  more  the  behavior  of  ions,  until  finally  the 
colloid  passes  over  into  a  crystalloid,  which  dissociates 


*  The  relations  existing  here  can  be  illustrated  also  by  examples  of 
protein  precipitation.  The  precipitation  of  protein  through  the  heavy 
metals  is  dependent  upon  the  neutralization  of  the  negative  protein 
through  the  positive  colloidal  metallic  hydroxide.  The  precipitates 
formed  are,  however,  not  soluble  to  the  same  extent  in  excesses  of  the 
individual  colloids.  The  silver-protein  precipitate  is,  for  example,  soluble 
in  an  excess  of  protein,  but  not  in  an  excess  of  the  silver  salt.  In  the 
former  case  we  have  to  do  with  the  formation  of  variable  aggregates' 
in  the  second  with  simple  neutralization  according  to  the  manner 
observed  by  Pick  on  his  toxostabile  sera  when  large  amounts  of  anti- 
toxin have  toxin  added  to  them. 


CHANGES   H  A'<  )i  ft .11 T  IN  PA THOLOG  Y.  12  1 

in  aqueous  solution  Into  its  strongly  charged  ions.  In 
this  way  mixtures  <>f  antagonistic  colloids  may  approx- 
imate in  their  properties  salts  thai  have  arisen  Erom 
combinations  between  weak  acids  and  weak  b 
Strictly  speaking,  we  arc  compelled  to  assume  the  existence 
of  at  least  traces  of  such  a  similarity  in  order  to  account 
for  the  traces  of  the  free  substances  which  we  find  beside 
the  aggregates  in  toxin-antitoxin  mixtures.  Some  toxin- 
antitoxin  mixtures  might,  finally,  because  of  their  close 
relationship  to  the  crystalloid  salts,  contain  the  free  sub- 
stances beside  completely  neutralized  aggregates.  Accord- 
ing to  the  investigations  of  Arrhenius  and  Madsen, 
it  is  not  impossible  that  such  a  state  of  affairs  exists 
in  the  case  of  their  tetanolysin.  We  arc  acquainted  with 
an  excellent  experimental  procedure  for  analyzing  col- 
loidal mixtures  which  Billitzer  has  employed  in  a  study 
of  the  relations  existing  in  mixtures  of  the  electropositive 
red  iron  hydroxide  and  the  electronegative  yellow  arsenious 
sulphide.  If  an  electric  current  is  sent  through  such 
a  mixture,  the  completely  neutralized  aggregates  do  not 
move,  while  the  unneutralized  aggregates,  which  carry 
the  electric  charge  of  the  colloid  that  is  present  in  excess, 
are  slowly  carried  to  the  oppositely  charged  pole.  The 
traces  of  free  colloid  still  present  move  most  rapidly 
and  to  opposite  poles,  where  they  evidence  themselves 
in  this  case  through  differences  in  color. 

The  transition  from  the  complicated  conditions  exist- 
ing in  the  case  of  the  toxins  to  the  more  simple  ones 
in  the  case  of  the  precipitating  and  agglutinating  sub- 
stances is  rendered  easy  through  the  fact  that  in  the 
latter  case  we  are  dealing  v  itli  the  reactions  of  the  rela- 
tively   well-understood    proteins,    or    substances    closely 


lit  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

related  to  them.     With  this  we  come  to  the  question  of 
the  colloidal  properties  of  the  proteins. 

If  an  electric  current  is  carefully  sent  through  a  solution 
of  egg  albumin  poor  in  salts,  the  protein  migrates,  as 
shown  by  chemical  analysis,  to  the  positive  pole.  This 
migration  is  very  slight,  and,  since  the  protein  particles 
have  been  by  optical  means  proved  to  be  very  small, 
must  be  attributed  to  a  weak  electronegative  charge 
which  they  carry.  A  current  of  250  volts  for  twenty-four 
hours  is  required  to  render  evident  this  migration  of  the 
protein.  The  slight  charge  and  the  minuteness  of  the 
particles  explain  the  very  considerable  stability  of  the 
protein  toward  precipitating  ions.  While  the  more 
strongly  charged  colloidal  metals  and  the  majority  of 
the  inorganic  colloids  are  precipitated  in  weak  salt  solu- 
tions, this  is  not  true  of  protein.  Through  this  fact  is 
rendered  possible  the  vitally  important  existence  of  salts 
and  protein  side  by  side.  If  the  protein  particles  are 
given  a  greater  charge  than  they  possess  normally, 
they  are  readily  precipitable.  In  the  presence  of  acids, 
for  example,  the  proteins  assume  a  strong  electropositive 
charge,  as  evidenced  by  their  very  considerable  migration 
toward  the  negative  pole,  and  are  now  readily  precipitable 
through  electronegative  colloids.  We  make  clinical  use 
of  this  procedure  daily  when  we  first  give  dilute  protein 
solutions  a  positive  charge  through  the  addition  of  acetic 
acid,  after  which,  upon  the  addition  of  potassium  ferro- 
cyanide,  they  produce  the  well-known  precipitate  with 
the  colloidal  negative  ferrocyanic  acid.  In  fact,  in  the 
majority  of  the  sensitive  reactions  for  albumin,  we  have 
to  do  with  the  effect  of  an  oppositely  charged  colloid 
upon  a  suitably  electrified  albumin. 


CHANGES   WROUGHT  IN  PATHOLOGY.  123 

The  phenomena  observed  in  precipitin  and  agglu- 
tinin reactions  are  explained  in  a  similar  way.  These 
precipitations  are  possible  only  in  the  presence  of  salts. 
If  the  protein  or  the  bacteria  under  investigation  arc- 
mixed  with  the  specific  substances  in  a  salt-free  condition, 
no  reaction  occurs.  These  specific  substances  may, 
therefore,  be  looked  upon  as  giving  the  colloidal  proteins 
the  properties  of  sensitive  colloids,  that  of  being  pre- 
cipitated through  small  amounts  of  salt  ions.  According 
to  Billitzer  the  specific  substances  serve  in  this  case 
only  to  give  the  colloidal  particles  the  charge  and  size 
necessary  for  precipitation.  Apparently  all  "  sensitizing  " 
reactions  encountered  in  the  realm  of  the  immune-body 
reactions  are  explainable  in  a  similar  way. 

A  phenomenon  frequently  observed  is  furnished  by  the 
above-mentioned  tendency  of  colloids  to  show  an  opti- 
mum proportion  in  which  the  two  reacting  colloids  must 
be  mixed  in  order  that  they  may  be  precipitated,  and  by 
the  inhibition  of  the  reaction  when  an  excess  of  the  one  is 
present.  Biltz  has  already  pointed  out  the  existence  of 
this  generalized  phenomenon  of  colloids  in  agglutination; 
analogous  phenomena  may,  however,  be  observed  in 
nearly  all  immune-body  reactions.  A  remarkable  exam- 
ple of  this  kind  is  furnished  by  the  "  complement  diver- 
sion "  (Komplcmcnlablcnkung)  observed  by  Neisser  and 
Wechsberg.  These  authors  showed  that  bactericidal 
immune  sera  showed  a  maximum  effect,  under  other- 
wise similar  conditions,  when  they  contained  a  medium 
amount  of  immune  substance.  No  doubt  we  can  with' 
profit  now  express  the  description  of  this  phenomenon 
in  the  smoother  language  of  colloid  chemistry.  The  com- 
plex relations  existing  in  the  case  of  haemolysis,   which 


124  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

may  be  brought  about  in  a  great  variety  of  ways,  also 
seem  clearer  as  soon  as  the  exit  of  the  coloring-matter 
from  the  blood-corpuscles  is  looked  upon  as  a  rupture 
of  the  colloidal  haemoglobin-stroma  compound.  There 
seem  to  exist,  therefore,  a  large  number  of  light-bringing 
relations  between  immunity  phenomena  and  phenomena 
in  colloid  chemistry.  Landsteiner  in  conjunction  with 
Jagic  have  been  able  to  show  the  identity  existing  between 
the  mechanism  of  the  haemolysis  (studied  by  Kyes  and 
Sachs)  brought  about  through  the  unknown  cobra  poison 
and  the  mechanism  of  the  hemolytic  effect  of  colloidal 
silicic  acid.  In  this  case  a  structurally  uniform  inorganic 
colloid  behaves  like  the  hsemolytic  amboceptor  of  the 
side  chain  theory. 

We  are  indebted  to  the  same  investigator  for  recog- 
nizing a  fact  of  still  more  general  significance.  The 
proteins,  and  from  many  facts  at  our  disposal  the  immune 
bodies  also,  represent  so-called  amphoteric  electrolytes; 
in  other  words,  substances  which  assume  basic  properties 
in  acid  solutions  and  acid  properties  in  alkaline  solutions; 
or,  as  shown  by  experiment,  change  the  sign  of  their 
electric  charge  with  a  change  in  reaction.  There  exists, 
however,  a  zone  between  the  extreme  changes  in  the 
sign  of  the  electrical  charge  in  which  these  hermaphrodite- 
like substances  respond  to  the  slightest  change  in  their 
surroundings  with  an  alteration  in  their  electrical  char- 
acter, through  which  the  existence  of  a  large  number  of 
finely  graded  relations  between  amphoteric  electrolytes 
differing  only  slightly  from  each  other  is  rendered  pos- 
sible. This  enormously  changeable  sensitiveness  of  such 
substances,  which  may,  according  to  circumstances,  act 
at  one  time  as  colloids   having   one  kind  of  electrical 


CHANGES   WROUGHT  IN  PATHOLOGY.  125 

charge,  al  another  time  an  <)])|io-itc  charge,  is  evidenced 
by  a  Large  number  of  facts.  With  this  conception  of 
the   r61e  of   amphoteric  substances,   Landsteiner   has 

made  the  in-!  rational  attempt  to  explain  the  specificity 
of  the  immune  substances. 

The  chemistry  of  the  colloids  also  allows  us  to 
assume  a  freer  position  regarding  the  hypotheses 
governing  investigations  in  immunity.  We  can,  how- 
ever, touch  upon  this  subject  only  briefly  here,  and 
must  limit  ourselves  to  the  question  of  toxins  and  anti- 
toxins. 

Every  one  is  familiar  with  the  dominating  influence 
which  those  views  have  at  present  attained  that  Ehrlich 
has  developed  under  the  name  of  the  side  chain  theory, 
views  which  have  not,  of  course,  remained  without  con- 
tradiction. The  opposition  which  this  theory  has  encoun- 
tered has  evidenced  itself  silently  in  the  fact  that  a  number 
of  investigators  have  continued  to  work  independently 
and  without  using  it,  and  audibly  through  the  ex- 
pressions of  various  authors,  .more  particularly  Max 
Gruber,  who  delivered  an  address  in  Vienna  several 
years  ago. 

As  already  stated,  Ehrlich  has,  among  others,  utilized 
the  fact  that  the  affinity  of  toxin  for  antitoxin  and  the 
toxicity  of  toxin  may  vary  independently  of  each  other 
to  support  the  idea  that  two  different  groups,  a  hapto- 
phorc  and  a  toxophore,  exist  in  a  toxin.  These  are 
supposed  to  furnish  the  material  substrate  for  the  different 
reactions  of  which  one  and  the  same  substance  is  capable. 
Ehrlich  has  at  the  same  time  distinguished  between 
different  varieties  of  a  toxin,  originating  in  part  from  the 
bacteria  themselves,  such  as  the  toxones,  and  in  part  the 


126  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

product  of  time  when  the  toxin  is  kept  for  a  long  time,  such 
as  the  toxoids.  The  differences  observed  in  the  toxicities 
of  a  toxin  when  only  partially  saturated  with  antitoxin, 
and  those  observed  in  the  behavior  of  different  animals 
toward  the  neutralized  toxins,  all  furnish  important 
support  for  these  assumptions.  But  we  must  look  upon 
it  as  a  fact  well  established  through  investigations  on 
colloids,  that  in  their  changes  in  state  a  part  of  their 
reactions  may  be  influenced,  while  another  part  may 
remain  untouched;  that  through  the  mixture  of  colloids 
which  neutralize  each  other  manifold  new,  in  no  sense 
preformed,  aggregates  can  be  produced,  and  that  such 
aggregates  may  at  one  time  allow  the  effect  of  the  one 
colloid, — in  this  case  the  toxin, — at  another  time  the  other, 
— the  antitoxin, — to  become  apparent.  Great  differences 
must  in  consequence  result  in  the  intensity  and  in  the 
picture  of  the  intoxication  in  different  animals.  Against 
Ehrlich's  theory  Arrhenius  and  Madsen,  as  well  as 
Gruber  and  Pirquet,  have  set  up  the  idea  that  in 
toxin-antitoxin  mixtures  we  always  have  to  do  with  a 
dissociation  of  compounds  having  only  a  weak  affinity 
for  each  other.  This  conception,  which  originated  from 
a  too  far-reaching  generalization  of  a  special  case,  allows 
only  of  the  existence  of  completely  neutralized  aggregates, 
beside  traces  of  their  components,  and  is,  therefore,  in- 
capable of  explaining  the  multitude  of  experimental  facts 
which  have  been  obtained  in  the  study  of  different  toxins, 
more  especially  diphtheria  toxin.  Against  this  inade- 
quate assumption  arose  the  strength  of  the  Ehrlich 
theory,  which  has  rendered  the  great  service  of  having 
been  the  first  to  fix  in  the  minds  of  investigators  the 
newly    discovered    and    scarcely    calculable    varieties   of 


CHANGES   WROUGHT  IN  PATHOLOGY.  1 27 

facts  won  through  a  study  of  immunity.  Bui  the  facts 
of  colloidal  chemistry,   together  with   advances   in  the 

investigation  of  immunity,  show  clearly,  it  seems  to  me, 
that  the  Eiirlich  assumptions,  in  spite  of  the  many 
variables  introduced  into  them,  do  not  at  all  suffice  to 
explain  the  phenomena  actually  observed. 

It  is,  for  example,  an  easy  matter  to  foretell  even  now 
that  through  changes  in  the  manner  and  the  rapidity  with 
which  toxin  and  antitoxin  are  mixed,  and  through  a 
proper  choice  of  animals,  the  varieties  of  toxins  that 
have  been  assumed  to  exist  by  Ehrlich  might  easily  be 
increased  indefinitely. 

It  can  be  readily  seen,  too,  how  difficulties  arise  in  the 
expansion  of  any  theory  that  is  based  upon  crystalloidal 
chemistry.  With  Ehrlich  it  is  the  application  of  syn- 
thetic organic  chemistry,  with  his  opponents,  the  appli- 
cation of  a  special  case  of  the  dissociation  of  salts  that 
finally  constitutes  too  narrow  a  frame  to  receive  the 
entire  picture  of  facts.  Insufficient  also  was  the  attempt 
of  DANysz  and  Bordet  to  explain  the  behavior  of  toxins. 
The  latter  especially  tried  in  his  brilliant  way  to  sup- 
port his  theory  through  an  analogy  with  the  process  of 
dyeing,  which  we  now  know  to  be  a  colloidal  reaction. 
In  this  theory  the  correct  assumption  that  toxin  and 
antitoxin  are  able  to  unite  in  different  proportions  was 
made;  it  could,  however,  be  of  value  only  as  a  hypo- 
thetical objection,  as  it  included  only  some  of  the  possi- 
bilities and  was  unable  to  explain,  while  lacking  the  broad 
base  of  other  facts  in  colloidal  chemistry,  the  variety  of 
observations  made  on  toxins.  If  we  disregard  my  first 
brief  suggestion,  pointing  out  the  relation  between  irii- 
munity  reactions  and  colloidal  changes  in  state,  LAND 


128  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

steiner  was  the  first  who  independently,  and  recogniz- 
ing the  goal  toward  which  he  was  travelling,  studied  this 
connection  between  immunity  and  colloidal  reactions 
experimentally.  Landsteiner  has  done  this  more  espe- 
cially for  agglutination  and  haemolysis,  while  I  have 
attempted  to  do  it  for  the  true  toxins  and  their  anti- 
toxins.* 

The  extensive  importance  of  colloidal  chemistry  for 
biology  is  by  no  means  limited  to  the  highly  interesting 
field  of  immunity.  This  can  be  shown  to  be  true  to- 
day, however,  on  only  a  few  examples. 

We  are  acquainted  with  a  remarkable  kind  of  separa- 
tion of  solid  colloids  through  the  action  of  surface  tension, 
an  understanding  of  which  is  of  importance  in  many 
problems  of  pathology. 

The  nature  of  these  forces  which  evidence  themselves 


*  I  am,  of  course,  aware  that  valuable  beginnings  have  already  been 
made  to  apply  the  facts  of  colloidal  chemistry  to  the  teachings  of  toxins 
and  antitoxins,  and  nothing  is  further  from  my  mind  than  to  disregard 
the  great  credit  which  more  especially  Biltz  deserves  in  this  respect.  I 
would,  nevertheless,  like  to  emphasize  that  my  conceptions  are  inde- 
pendent ones  which  developed  gradually — as  such  things  must — in 
the  course  of  my  investigations  of  organic  colloids.  They  form  only 
a  special  case  of  the  analogy  which  I  have  for  more  than  a  decade 
tried  to  show  exists  in  the  most  varied  subjects  between  changes  in  the 
state  of  colloids  and  the  processes  that  go  on  in  living  matter.  My 
treatment  of  the  subject  is,  moreover,  directed  toward  numerous  until 
now  scarcely  prized,  but  apparently  most  important,  sections  of  the 
problem. 

For  the  parallelism  between  the  precipitation  of  a  colloid  and  the 
neutralization  of  a  toxin  by  an  antitoxin  which  I  have  given  above, 
the  experiments  of  Coehn,  according  to  whom  toxin  and  antitoxin 
wander  toward  the  same  side  in  the  electric  current,  are  of  no  importance, 
as  I  have  been  able  to  show  in  my  unequivocal  investigations. 


CHANGES   WROUGHT  IN  PATHOLOGY.  129 

at  the  surfaces  of  all  liquids  is  familiar  to  every  one. 
While  the  particles  within  the  liquid  are  surrounded  on 

all  sides  by  particles  of  the  same  kind  and  arc  in  con- 
sequence in  a  state  of  equilibrium  through  the  uniform 
distribution  of  the  attractive  forces  about  them,  this  is 
not  the  case  with  the  surface  particles.  For  here  the 
forces  which  act  upon  the  particles  and  are  directed 
toward  the  centre  of  the  liquid  encounter  no  correspond- 
ing antagonistic  force.  In  consequence  of  the  effort  of 
the  surface  particles  to  follow  the  attraction  toward  the 
centre,  the  surface  endeavors  to  become  as  small  as 
conditions  will  permit.  Many  substances  are  able 
through  solution  in  a  solvent  to  bring  about  a  decrease- 
in  its  surface  tension.  Under  these  circumstances  the 
liquid  may  follow  its  tendency  to  decrease  its  surface  as 
much  as  possible  by  allowing  the  particles  of  the  sub- 
stance which  decrease  the  surface  tension  to  take  the 
place  of  the  particles  of  the  liquid  which  arc  being  pulled 
toward  the  centre.  In  this  way  the  surface  becomes 
gradually  richer  in  the  dissolved  substance.  In  the  end 
the  concentration  of  the  solid  particles  at  the  surface 
becomes  so  great  that  a  film  is  formed  which  may  be 
removed  and  which  is  renewed  after  each  removal.  This 
behavior,  which  has  been  studied  in  great  detail  by 
Ramsden,  is  shown  chiefly  by  the  colloids,  more  especially 
protein  solutions.  If  such  solutions  are  shaken  together 
with  air  or  immiscible  liquids,  such  as  oil,  chloroform,  or 
mercury,  all  the  dissolved  colloid  can  finally  be  precipi- 
tated through  the  surfaces  which  are  constantly  re- 
newed. 

That  this  process  should  be  demonstrable  most  clearly 
on  colloids  and  especially  on  protein  solutions  is  due  to 


13°  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

two  still  other  conditions,  according  to  our  judgment. 
If  the  coagulation  through  surface  tension  is  studied  in 
detail  we  find  that  we  have  to  do  with  an  extreme  increase 
in  the  concentration  of  a  solution,  or,  what  amounts  to 
the  same  thing,  with  the  expression  of  the  solvent  from 
such  a  solution.  The  energy  necessary  for  this,  which, 
as  is  well  known,  expresses  itself  in  osmotic  pressure,  is, 
however,  in  the  case  of  the  colloidal  substances,  exceed- 
ingly small  in  contrast  to  that  observed  in  crystalloidal 
substances.  And  so  it  is  that  the  colloids  are  especially 
well  able  to  form  solid  surface  films  quickly  and  exten- 
sively. 

A  second  important  condition  is  the  electrical  charge 
of  the  colloidal  particles.  The  greater  this  is,  the 
more  powerful  are  the  repellent  forces  between  the  sim- 
ilarly charged  particles  that  antagonize  the  surface  ten- 
sion, which  tends  to  crowd  them  together.  The  proteins, 
as  we  know,  carry  only  weak  charges  of  electricity  and 
furnish  in  consequence  favorable  conditions  for  the  col- 
lection of  the  particles  on  free  surfaces.  To  the  formation 
of  such  solid  protein  films  Ramsden  attributes  the  well- 
known  formation  of  a  film  on  milk  and  the  behavior  of 
the  fat  droplets  of  milk,  which  have  long  been  imagined, 
from  their  physical  and  chemical  reactions,  to  be  sur- 
rounded by  a  denser  film  of  protein.  In  pathology  similar 
phenomena  might  play  an  accessory  part  in  air  and  fat 
embolism.  It  can  readily  be  shown  experimentally  that 
the  migration  of  air  bubbles  in  tubes  which  are  filled 
with  protein  solutions  meets  with  unexpectedly  great 
difficulties.  In  the  living  organism  the  danger  of  the 
entrance  of  air  bubbles  or  fat  droplets  into  the  circulation 
js  dependent,  at  least  in  part,  upon  similar  processes. 


CHANGFS   WROUGHT  IN  PATHOLOGY.  13  * 

In  both  cases  we  have  to  d<>  with  a  solidification  of  their 
surfaces  which  makes  the  emboli  behave,  in  spite  of  their 

gaseous  or  liquid  character,  like  solid  obstructions  to  the 
circulation. 

In  a  new  light  appear  also,  through  a  study  of  the 
colloids,  the  extracellular  phenomena  observed  in  the 
development  of  solid  supporting  substances,  such  as  car- 
tilage and  bone,  and  the  precipitation  of  crystalloidal  sub- 
stances in  the  tissues  connected  with  them.  The  latter 
question,  which  is  also  of  great  pathological  importance, 
has  aroused  much  interest  in  the  past  decade,  but  it  does 
not  seem  to  have  been  possible  to  get  far  beyond  the 
recognition  of  the  difficulties  which  the  solution  of  the 
problem  encounters.  The  nucleus  of  the  question  seems 
to  lie  in  the  fact  that  we  are  dealing,  on  the  one  hand, 
with  simple  processes  of  crystallization,  while,  on  the 
other  hand,  formative  influences  on  the  part  of  the  cells 
and  functional  adaptations  to  the  forces  destined  to  act 
upon  them  seem  to  be  clearly  discernible  in  the  arrange- 
ment of  the  crystallization.  Besides  the  studies  of  nu- 
merous investigators  on  the  process  of  ossification,  it  has 
been  Biedermann,  more  especially  within  recent  years, 
who,  through  his  excellent  work  on  the  shells  of  molluscs, 
crustaceans,  and  insects,  has  furnished  much  important 
experimental  material. 

The  importance  of  colloidal  chemistry  in  these  prob- 
lems evidences  itself  at  once  in  that  first  and  most  important 
question  of  the  conditions  under  which  the  scarcely 
soluble  salts  are  kept  in  solution  and  precipitated  in 
suitable  places.  The  colloids  constitute,  as  shown  by 
many  experiments,  an  excellent  means  under  certain 
circumstances  of  keeping  slightly  soluble  salts  in  solution, 


132  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

in  that  they  themselves  unite  with  the  salt  ions  and  form 
aggregates  without  necessarily  being  precipitated,  when 
the  size  and  charge  of  the  particles,  as  in  the  case  of 
protein,  are  small.  It  is,  for  example,  an  easy  matter 
to  show  that  by  no  means  inconsiderable  amounts  of 
barium  sulphate,  one  of  the  least  soluble  of  substances, 
can  be  kept  in  solution  in  serum.  If  now,  through  the 
metabolism  of  the  cells,  the  dissolving  colloids  are  de- 
stroyed and  not  replaced,  supersaturation  and  finally 
precipitation  of  the  crystalloidal  material  can  easily  be 
brought  about,  after  which,  as  is  so  often  the  case,  crystals 
that  have  once  been  formed  may  serve  as  centres  for 
further  crystallization.  This  conception  seems  to  make 
clear  the  connection  between  crystallization  and  the  vital 
activities  of  the  cells,  as  evidenced  by  the  organization 
of  the  supporting  tissues.  It  renders  intelligible  also  the 
regularly  observed  phenomenon  that  a  small  portion  of 
colloidal  material,  which  is  no  longer  able  alone  to  keep 
the  salts  in  solution,  always  crystallizes  out  with  them. 
In  this  same  direction  is  to  be  sought  the  connection 
between  pathological  processes  of  calcification,  deposition 
of  uric  acid,  and  tissue  metabolism.  If  the  beautiful 
investigations  of  Paul  and  His  on  the  conditions  deter- 
mining the  solubility  of  uric  acid  are  not  of  that  im- 
portance for  the  pathogenesis  of  gout  which  they  had 
hoped,  then  this  is  dependent  primarily  upon  the  fact 
that  the  same  conditions  of  equilibrium  which  exist  in 
the  organism  in  the  presence  of  colloids  were  not  estab- 
lished in  their  experiment. 

A  special  problem  is  presented  by  the  origin  of  the 
great  solidity  of  cartilage  and  bone,  or  rather  their 
peculiar  colloidal  intercellular  substance.     These  tissues 


CHANGES   WROUGHT  IN  PATHOLOGY  133 

possess  a  characteristic,  highly  concentrated  ground  sub- 
stance, connected  with  structures  which  represent,  in 
the  main,  thin  layers  deposited  abcut  the  formative  cells 
or  their  delicate  protoplasmic  extensions.  A  very  in- 
structive example  of  this  kind  is  furnished  by  the  exceed- 
ingly hard  cartilage  of  myxina,  in  which  Schaffer  was 
recently  abl«°  to  demonstrate  layers  of  great  delicacy  sur- 
rounding the  cartilage  cells.  In  such  thin  precipitation 
layers  there  can  arise,  when  they  absorb  or  gradually 
give  off  water,  tremendous  pressures  which  might  well  be 
of  great  importance  in  hardening  the  entire  mass.  Ac- 
cording to  experiments  which  I  have  carried  out  in  conjunc- 
tion with  Dr.  Ludwig  Mach,  it  is  an  easy  matter  to  give 
protein  a  bony  hardness  by  pressing  it  into  a  steel  tube 
and  heating  it  almost  to  its  decomposition  temperature. 
Interestingly  enough,  this  ability  to  form  a  material 
sufficiently  hard  to  be  worked  with  instruments  is  con- 
nected with  a  certain  integrity  of  the  albuminous  sub- 
stance and  is  lost  entirely  when  the  albumin  is  decomposed 
beyond  the  albumose  stage.  By  mixing  with  the  protein 
the  fine  dust  of  insoluble  calcium  salts  in  the  proportion 
in  which  these  are  found  in  bone,  the  solidity  of  the  prod- 
uct can  be  markedly  increased. 

The  pressures  exerted  by  thin  layers  of  colloid  under 
suitable  circumstances  cannot  well  be  determined.  That 
these  may  attain  high  value  is  shown  by  experiments  of 
Catlletet,  who  was  able  to  render  glass  permanently 
doubly  refracting  through  thin  layers  of  gelatine  which 
were  allowed  to  dry  upon  its  surface. 

With  this  example,  to  which  many  others  might  be 
added,  illustrating  the  connection  between  physico- 
chemical   investigations   and   morphology,   I   shall  close 


134  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

what  I   intended  to  offer  in  the  line  of  experimental 
facts. 

If  I  have  succeeded,  as  I  hope,  in  convincing  you  also 
that  the  application  of  colloidal  chemistry  to  physiology 
and  pathology  justifies  great  expectations,  it  might  be  well, 
in  conclusion,  to  seek  in  the  development  and  the  present 
state  of  the  colloid  problem  a  measure  for  our  faith  in 
its  future  contributions. 

As  is  well  known,  the  difference  between  crystalloids 
and  colloids  appeared  to  be  so  radical  a  one  to  Graham 
that  to  characterize  it  he  wrote  the  following  oft- quoted 
sentence : 

"  The  difference  between  these  two  kinds  of  matter  is 
like  that  which  exists  between  the  material  found  in  a 
mineral  and  that  found  in  an  organized  mass." 

The  discoverer  of  the  colloidal  world  has  since  been 
reproached,  and  certainly  unjustly,  for  having  so  strongly 
emphasized  the  differences  between  crystalloids  and  col- 
loids. For  every  discovery  depends  primarily  upon  a 
recognition  of  the  most  apparent  differences  between  the 
new  phenomenon  and  the  facts  well  known  at  the  time. 
This  contrast  is  the  most;  powerful  stimulus  to  investi- 
gation. It  is  the  source  of  the  problem,  which  is  not 
solved  until  the  apparent  contradictions  to  it  have  been 
set  aside  and  those  fine  threads  have  been  unravelled 
which  connect  the  newly  found  with  the  old.  Our  prob- 
lem also  developed  in  this  way,  and  we  have  seen  how 
the  connection  between  colloids  and  crystalloids  was 
established  through  a  recognition  of  their  principal 
characteristics  and  their  gradations.  One  is  almost 
inclined    to    believe   that    the    possibility  of    explaining 


CHANCES  WROUGHT  IN  PATHOLOGY  135 

organized  living  matter  through  his  colloidal  condition 
seemed  close  at  hand  even  to  Graham. 

The  continued   application  of  colloidal   chemistry   to 
biological  problems  soon  shows,  however,  the  limits  which 

arc  set  upon  it.  We  are  able  to  see  this  in  the  ca 
the  antibodies  also.  How  much  a  knowledge  of  the 
colloids  contributes  toward  an  understanding  of  their 
varied  reactions  and  even  the  solution  of  the  riddle  of 
their  specific  sensitiveness  toward  each  other  seems  most 
apparent.  Our  new  methods  are  of  no  use,  however, 
as  soon  as  we  try  to  discover  the  secret  mechanism  by 
means  of  which  the  cells  produce  a  suitable  antitoxin 
against  any  definite  toxin.  To  repeat  the  words  of 
Gruber:  "  Whence  comes  this  astonishing  purposeful- 
ness,  this  predetermined  harmony,  this  specific  adapta- 
tion of  substance  to  antisubstance,  which  one  would 
a  priori  consider  entirely  impossible?" 

It  must  seem  remarkable  that,  instead  of  exhausting 
one's  self  in  chemical  analogies,  one  has  not  sought  a  more 
intimate  connection  *  with  those  phenomena  which  arise 
from  a  direct  observation  of  living  matter.  Beginning 
with  his  classical  investigations  of  the  physiology  of  the 
senses,  Ewald  Hering  has  developed  a  theory  of  the 
changes  that  go  on  in  living  matter,  which  through  abun- 
dant use  of  the  principle  of  mobile  equilibrium  has  fore- 
shadowed modern  chemical  dynamics.  We  need  only  to 
recall  how,  according  to  Hering,  the  sensations  of 
antagonistic  colors  correspond  with  antagonize  reactions 
in  the  visual  substance  which  mutually  suppress  each 
other.     When   we   consider   that   the  substances  of  the 

*  <  >iil\  I.  wpstkinicr  makes  a  simil  ir  suggestion. 


I36  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

red  process  produce  in  their  surroundings  or  after  them 
the  antibodies  of  the  green  process,*  and  that  these  prod- 
ucts neutralize  each  other  physiologically,  just  as  do  toxin 
and  antitoxin,  the  analogy  between  the  two  phenomena 
becomes  very  apparent. 

In  spite  of  a  few  differences,  are  not  the  chemical  phe- 
nomena of  the  production  of  a  lasting  complementary 
after-image  and  the  formation  of  an  antitoxin  essentially 
the  same?  Even  in  Ehrlich's  bold  conception  of  the 
regenerative  hyperplasia  of  the  side  chains,  there  seems 
to  be  mirrored  only  a  part  of  that  truth  which  Hering 
grasped  so  deeply. 

No  doubt  every  attempt  to  follow  these  questions 
further  soon  brings  us  to  the  solid  barriers  of  our  present 
knowledge,  which  do  not  open  even  to  the  storm  of 
physical  chemistry.  And  if  some  investigators,  such  as 
the  followers  of  the  energetic  school,  carried  away  by 
physical  chemistry,  have  believed  that  they  had  hoisted 
their  flag  upon  the  outermost  pole  of  biology,  it  has 
always  been  found  that  this  was  due  to  a  failure  to  dis- 
criminate between  the  boundaries  of  the  known  and  the 
unknown.  We  have  therefore  learned  to  be  satisfied 
with  having  arrived  at  a  clear  conception  of  the  problem 
before  us,  just  as  the  chemist  who  must  first  carefully 
free  an  unknown  substance  of  all  its  impurities  before 
he  holds  the  pure  crystal  in  his  hands.     As  yet  the  way 


*  For  comparison  the  white-black  process  might  better  be  used,  because 
this  leads  to  black  in  only  one  direction,  namely,  over  white  to  black. 
In  the  case  of  the  antibodies  also  we  obtain  the  antibody  only  by  way 
of  the  toxin  and  not  conversely.  The  exceptions  mentioned  in  the 
sentence  following  the  one  to  which  this  note  refers  have  to  do  with 
another  point  which  will  be  discussed  in  detail  at  some  future  time. 


ON  THE  ELECTRICAL   CHARGE   Of  PROTEIN.      137 

is  not  apparent  along  which  it  will  one  day  become 
possible  to  discover  its  structure. 

7.   On  the  Electrical  Charge  of  Protein  and  its 
Significance.* 

I. 

The  surprising  development  of  the  chemistry  of  the 
colloids,  which  in  no  small  part  has  been  incited  through 
its  great  biological  importance,  has  reacted  most  benef- 
icently upon  the  latter  science  and  many  problems  in 
general  physiology.  I  have  repeatedly  had  the  honor 
of  bringing  before  this  society  reports  of  that  daily 
increasing  territory  in  which  the  study  of  colloidal  reac- 
tions touches  upon  or  coincides  with  that  of  the  struc- 
ture and  changes  in  state,  and  in  consequence  the  func- 
tions of  the  cells  and  fluids  of  the  organism. 

If  one  attempts  to  survey  the  long  series  of  colloidal 
substances  and  to  study  along  the  lines  common  to  all, 
it  must  become  apparent  to  every  one  how  markedly 
their  typical  properties  vary  in  degree  in  spite  of  a  certain 
identity  in  behavior  in  the  matter  of  diffusion,  for  example; 
and  how  the  presence  or  entire  absence  of  certain  prop- 
erties changes  the  whole  character  of  a  colloidal  reaction. 
This  holds  not  only  for  the  fundamental  differences 
between  the  solid  and  jelly-like  colloids,  or  gels,  and  the 
liquid  colloids,  or  sols,  but  also  for  the  individual  mem- 
bers of  each  of  these  groups.  In  fact,  we  see  that  among 
the  sols  the  proteins  constitute  an  almost  independent 

*  From  Naturwissenschaftliche  Rundschau,  moo.  XXI,  p.  3.  Ad- 
dress delivered  before  the  Morphologisch-physiologische  Gesellschaft  in 

Vienna,  December  5,  1905. 


138  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

group  because  of  numerous  properties  that  they  have 
in  common.  This  behavior  will,  no  doubt,  have  to  be 
taken  into  consideration  by  any  one  who  attempts  to 
extend  the  analogy  of  the  behavior  of  colloids  in  general 
to  that  of  the  colloidal  substances  in  the  fluids  and  tissues 
of  the  organism.  For  it  has  been  found  that  the  reactions 
of  all  colloids  do  not  approximate  the  reactions  that 
occur  in  the  living  body,  in  consequence  of  which  it  has 
proved  necessary,  in  the  attempt  to  discover  such  anal- 
ogies, to  cling  to  the  colloidal  products  of  living  matter 
itself,  namely,  to  the  proteins. 

The  value  of  a*n  accurate  knowledge  of  the  proteins 
as  a  means  of  understanding  the  inner  workings  of  life 
phenomena  has  at  different  times  been  differently 
estimated  by  physiologists.  While  a  time  once  existed 
when  many  believed  that  a  knowledge  of  protein  structure 
would  by  itself  give  us  an  explanation  of  the  peculiar 
metabolism  of  living  matter,  we  have  to-day,  when  the 
beginnings  of  a  protein  synthesis  are  apparent  and  many 
important  constituents  of  the  protein  molecule  have  been 
isolated,  become  quieter  and  soberer  in  our  expectations. 
Largely  independent  of  a  complete  insight  into  the 
chemical  composition  of  the  proteins  is  the  knowledge 
of  their  physico-chemical  properties,  which  can  only  be 
obtained  through  utilization  of  different  methods.  This 
knowledge  gives  us  an  immediate  understanding  of  the 
majority  of  the  general  properties  and  functions  of  the 
tissue  fluids,  and  is  applicable  without  reserve  to  those 
cases  also  in  which  no  longer  living  but  more  or  less 
coagulated  cell  material  serves  as  an  object  of  research. 
In  the  end,  however,  such  a  knowledge  also  renders  easy 
an  insight  into   the   changes   that   take  place  in  living 


ON   THE  ELECTRICAL   CHARGE  OF  PROTEIN.        139 

cells  in  consequence  of  the  frequently  recognizable  paral- 
lelism between  changes  in  state  in  colloids  and  changes 

in  physiological  function.  This  is  no  doubt  dependent 
upon  the  fact  that  the  colloidal  constituents  of  living 
matter  show,  at  least  in  part,  a  physico  chemical  identity 
with  the  properties  of  isolated  proteins. 

It  is  our  purpose  to  day  to  give  as  far  as  possible  a 
survey,  based  on  the  personal  investigations  of  many  years, 
of  the  more  important  physico-chemical  properties  of  the 
proteins,  and  to  point  out,  at  least  in  a  cursory  way,  the 
relation  between  these  properties  and  many  biological 
phenomena. 

II. 

As  in  the  case  of  crystalloids,  so  both  the  behavior  in 
solution  and  the  behavior  in  the  solid  precipitate  serve 
to  characterize  the  colloids.  An  accurate  knowledge  of 
the  conditions  which  determine  their  precipitation  has 
recently  assumed  great  importance  in  the  study  of  the 
colloids. 

We  can  to-day  regard  it  as  settled  that  between  a  true 
suspension  and  a  colloidal  solution  there  exists  only  a 
difference  in  the  size  of  the  suspended  particles.  In  a 
colloidal  solution  they  are  always  so  small  that  through 
their  friction  upon  each  other  they  are  kept  in  suspension. 
The  colloidal  particles  seem,  therefore,  to  be  no  longer 
affected  by  the  force  of  gravity,  just  as  i>  the  case  with 
those  smallest  dust  particles  in  the  air  that  become  visible 
onlv  in  the  sunlight.  The  colloidal  particles  can  also  be 
rendered  visible  in  many  cases  by  utilizing  intense  illu- 
mination methods.  Even  though  gravity  is  unable  to 
cause  a  clumping  of  the  colloidal  particles,  other  forces 


140  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

are  readily  able  to  do  so,  especially  electrostatic  forces, 
with  which  we  are  going  to  deal  chiefly  to-day. 

As  is  well  known,  many  crystalloids,  such  as  salts,  acids, 
and  bases,  give  off  their  constituents  at  the  electrodes 
when  a  current  is  sent  through  them.  We  call  such  sub- 
stances'electrolytes,  and  a  much-used  theory  assumes,  as 
is  well  known,  that  there  exist  in  aqueous  solutions  of 
electrolytes,  besides  the  electrically  neutral  molecules,  the 
electrically  charged  dissociation  products,  the  so-called 
ions.  Upon  the  migration  of  these  ions  toward  the 
electrodes  is  dependent  the  conduction  of  electricity.  The 
ions  are  said  to  be  positive  when  they  wander  to  the 
negative  pole  to  be  discharged  and  deposited,  and  negative 
when  they  wander  to  the  positive  pole.  In  this  way  the 
H  ion,  which  all  acids  have  in  common,  is  electropositive, 
the  remaining  portion  of  the  molecule  electronegative, 
In  the  same  way  the  OH  ion,  which  all  alkalies  have  in 
common,  is  electronegative.  The  strength  of  an  acid 
or  a  base  is  determined  by  the  concentration  of  these 
ions. 

Colloids  behave  in  an  entirely  different  way.  If  an 
electric  current  is  sent  through  a  pure  colloidal  solution, 
the  colloidal  particles  move,  in  contrast  to  the  electrolytes, 
in  only  one  direction.  They  accumulate  at  either  the 
positive  or  negative  electrode,  from  which  we  conclude 
that  they  have  either  a  negative  or  a  positive  charge.  A 
connection  has  shown  itself  to  exist  between  this  electrical 
charge  and  the  process  of  precipitation.  Several  inves- 
tigators, more  especially  Biltz,  have  shown  that  only 
oppositely  charged  colloids  mutually  precipitate  each 
other,  and  that  the  entirely  precipitated  colloidal  material 
no  longer  has  an  electrical  charge,  that  is  to  say,  no 


ON   THE  ELECTRICAL   CHARGE  OE  PROTEIN.        Mi 

longer  moves  with  the  electric  current.  Even  before 
Biltz's  work  other  observations  had  indicated  the  impor 
tance  of  electrical  conditions  for  colloidal  precipitations 
and  had  formed  the  starting-point  of  theoretical  explana- 
tions. The  colloids  seem,  in  general,  to  be  precipitable 
only  through  electrolytes;  non  electrolytes  such  as  sugar 
or  urea  have  no  precipitating  effect  even  upon  very  un- 
stable colloids.  1  Iakdy  and  BREDIG  have,  in  accord  with 
the  theory  of  elect rocapillary  phenomena,  developed  the 
idea  that  there  exists  an  antagonism  between  the  forces 
of  surface  tension,  which,  according  to  Bredig,  cause 
the  colloidal  particles  to  coalesce,  and  the  electrical  charges 
that  the  colloidal  particles  carry,  in  such  a  way  that  only 
after  the  electrical  charge  which  causes  the  particles  to 
repel  each  other  has  been  removed  can  the  surface  tension 
attain  its  maximum.  If  a  discharge  of  the  colloidal 
particles  is  brought  about  through  the  addition  of  the 
oppositely  charged  ions  of  electrolytes,  then  the  optimum 
of  precipitability  is  produced  at  the  same  time,  and  a 
precipitate  is  formed. 

According  to  a  different  theory  developed  by  Billitzer, 
surface  tension  does  not  play  the  role  attributed  to  it  by 
Hardy  and  Bredig.  If  oppositely  charged  ions  are 
added  to  a  colloid,  the  colloidal  particles  collect  about 
these  ions  through  electrostatic  attraction.  In  this  way 
aggregates  are  finally  formed  of  sufficient  size  to  fall  to 
the  bottom.  According  to  this  view,  with  which  many 
facts  agree  that  contradict  the  first-mentioned  theory,  a 
colloid  carrying  no  electrical  charge  should  be  capable 
of  precipitation  only  with  difficulty,  as  its  particles  exert 
no  electrostatic  forces.  One  can  regard  these  theories 
a§    "ne    pleases;    no   doubt    the    necessity    of    testing    the 


142  PHYSICAL    CHEMISTRY  IN  MEDICINE. 

electrical  behavior  of  dissolved  protein  in  order  to  obtain 
a  better  insight  into  its  colloidal  reactions  will  be  apparent 
to  every  one.  I  planned,  therefore,  to  obtain,  first  of  all, 
native  protein  as  free  from  electrolytes  as  possible  in 
order  to  have  a  stock  material  for  testing  the  effect  of 
different  conditions  upon  the  electrical  behavior  of  pro- 
tein. From  the  standpoint  of  general  technic,  moreover, 
it  seemed  of  great  value  to  use  a  material  which  through 
extreme  dialysis,  or  this  in  combination  with  repeated 
freezing,  had  been  rendered  as  free  from  salts  as  possible. 
The  electrical  conductivity  rendered  possible  through 
the  presence  of  ions  is  very  great  when  compared  with 
that  produced  through  the  migration  of  colloids.  In 
order  to  render  the  latter  apparent,  very  strong  currents 
must  therefore  be  used,  which  in  the  presence  of  salts 
lead  to  a  great  heating  of  the  solution  and  also  to  a 
masking  of  the  phenomenon  sought  for  through  the 
action  of  the  products  of  electrolysis.  In  our  experiments 
we  used,  for  example,  a  current  of  250  volts  and  6  amperes. 
In  this  current  ordinary  blood  serum  burns,  while  our 
salt-free  serum  allowed  only  a  few  millionths  of  the 
current  to  pass  through  it.  To  test  the  migration  of  the 
colloid  in  the  electrical  current  we  utilized  an  apparatus 
similar  to  the  one  successfully  used  by  Billitzer  in  his 
beautiful  experiments.  Three  beakers  of  uniform  size 
were  connected  with  each  other  by  means  of  siphons. 
The  electrodes  dipped  into  the  two  outer  beakers,  while 
the  middle  one  served  as  a  control,  the  contents  of  which 
should,  of  course,  not  vary.  At  the  conclusion  of  the 
experiment  the  nitrogen  in  all  three, of  the  vessels  was 
determined  by  Kjeldahl's  method. 

The    results  of  a  long  series  of  electrical  convection 


ON   THE  ELECTRICAL   CHARGE  OF  PROTEIN.        M3 

tests,  in  which  tin-  effect  of  concentration  and  other  con- 
ditions was  also  determined  quantitatively,  may  be  thus 
summarized: 

i.  A  protein  which  has  been  carefully  freed  from 
electrolytes  shows  no  recognizable  electrical  charge  and 
docs  not  wander  toward  one  of  the  two  electrodes,  even 
when  subjected  to  an  electric  current  for  twenty-four 
hours. 

2.  Each  of  the  albuminous  constituents  of  the  scrum — 
serum  albumin,  pseudoglobulin,  euglobulin — shows  no 
electrical  charge  in  the  absence  of  electrolytes. 

3.  The  addition  of  neutral  salts  of  the  alkalies  or  the 
alkaline  earths  does  not  impart  an  electrical  charge  to 
the  uncharged  protein. 

4.  Traces  of  acids  impart  a  positive  charge  to  protein 
through  their  positively  charged  hydrogen  ions;  alkalies 
a  negative  charge  through  their  hydroxyl  ions. 

5.  Salts  with  an  alkaline  reaction  toward  litmus,  such 
as  carbonates  and  the  secondary  and  tertiary  phosphates 
of  the  alkali  metals,  render  protein  electronegative;  acid 
salts  give  it  a  positive  charge. 

6.  This  charge  is  independent  of  the  end  reaction  of 
the  medium.  A  proper  mixture  of  protein  and  sodium 
bicarbonate  is  faintly  acid  toward  phenolphthalein,  neutral 
toward  litmus;  the  protein  has,  however,  a  strongly 
negative  charge. 

III. 

Let  us  consider,  first  of  all,  the  fact  that  our  salt-free 
protein  carries  no  electrical  charge.  How  does  it  behave 
toward  the  salts  of  the  heavy  metals,  such  as  Cu,  Fe,  Zn, 
Pb,  Hg,  which  are  all  regarded  as  general  precipitants  of 


144  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

protein  in  even  very  dilute  solutions  ?  All  these  salts  are 
characterized  by  the  fact  that  they  undergo  great  hydro- 
lytic  dissociation  in  dilute  solution — in  other  words,  take 
up  water  and  break  up  into  their  metallic  hydroxide  and 
their  acid.  According  to  different  investigations  which 
agree  in  their  conclusions,  the  dissolved  colloidal  electro- 
positive metallic  hydroxide  is  the  real  protein-precipi- 
tating constituent.  If  now  it  is  true  that  colloids  mutually 
precipitate  each  other  only  through  the  opposite  electrical 
charges  which  they  carry,  then  the  uncharged  protein 
should  in  general  not  be  precipitable  through  electro- 
positive heavy  metals.  It  can  be  easily  shown  that  our 
uncharged  protein,  in  contrast  to  native  protein,  cannot 
be  precipitated  through  salts  of  Fe,  Cu,  Hg,  Pb,  and  Zn. 
This  experiment  harmonizes,  therefore,  with  Billitzer's 
theory,  according  to  which  protein  is  very  stabile  in  the 
uncharged  state. 

Let  us  now  turn  to  something  else.  As  is  well  known, 
alcohol  is  an  excellent  precipitant  for  proteins.  Since 
alcohol  as  a  non- electrolyte  furnishes  practically  no  ions 
in  aqueous  solution,  its  precipitating  power  cannot  rest 
upon  electrical  grounds.  The  matter  may  be  explained 
in  the  following  way :  Proteins  are  not  soluble  in  alcohol, 
but  they  are  readily  miscible  with  water.  The  proteins 
are  therefore  crowded  out  of  their  solvent  through  the 
addition  of  much  alcohol,  in  the  course  of  which  their 
small  particles,  by  virtue  of  their  surface  tension,  coalesce 
into  larger  aggregates  in  a  way  similar  to  the  clumping  of 
the  particles  of  a  fresh,  fine  precipitate  into  larger  masses 
with  time.  We  will  therefore  not  be  surprised  to  see 
that  our  uncharged  protein  is  readily  precipitated  by 
alcohol.     But  what  will  happen  if  we  first  give  this  protein 


ON   THE  ELECTRICAL   CHARGE  OF  PROTEIN.       MS 

a  positive  or  a  negative  charge?  We  create  in  this  way 
repellent  electrical  forces  between  the  smallest  particles 
of  colloidal  material,  which  will  work  against  the  surfai  e 
tension,  which  tends  to  make  them  coalesce  and  pre 
cipitate.  If  the  protein  Is  given  an  electrical  charge 
through  the  addition  of  a  little  acid  or  alkali,  then,  as 
experiment  shows,  its  precipitation  through  alcohol  is 
inhibited  or  entirely  prevented.  We  may  imagine  from 
this  that  for  precipitation  through  non-electric  forces 
conditions  must  exist  somewhat  similar  to  those  which 
Hardy  and  Bredig  believed  to  exist  for  electrolytes. 

In  passing  it  may  be  mentioned  that  our  uncharged 
protein  is  readily  coagulable  through  heat  and,  as  may 
be  imagined,  through  acetic  acid-potassium  ferrocyanide, 
phosphotungstic  acid,  and  phosphomolybdic  acid.  In 
the  first  case  we  are  dealing  with  an  as  yet  not  entirely 
understood  chemical  change  in  the  protein  brought  about 
through  the  high  temperature.  In  the  second  case  the 
protein  is  first  charged  positively  through  the  acetic  acid, 
to  be  precipitated  later  by  the  various  oppositely  charged, 
probably  colloidal,  acid  ions. 

These  conversion  and  precipitation  experiments  are 
able  to  answer  the  question,  In  what  electrical  condition 
do  the  proteins  exist  in  the  blood  and  the  tissue  fluids? 
Since  alkalies  impart  a  negative,  acids  a  strongly  positive, 
reaction  to  proteins,  one  is  able  to  draw  conclusions  from 
the  reactions  of  animal  fluids  as  to  the  charge  of  the 
proteins  contained  in  them.  Modern  investigations  have 
solved  for  us  the  question  of  the  reaction  of  the  tissue 
fluids,  or,  to  put  it  more  accurately,  the  relation  between 
their  content  of  H  and  OH  ions.  According  to  these 
investigations,    the   body    fluids    are    neutral.     The    free 


146  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

hydrogen  and  hydroxyl  ions  exist  in  them  in  the  same 
proportion  as  in  water.  This  is  shown  most  harmoni- 
ously not  only  through  tests  with  proper  indicators, 
such  as  phenolphthalein,  but  also  through  electrical 
measurements.  Litmus,  which  was  formerly  employed 
as  an  indicator,  is  itself  too  strong  an  acid  to  show 
the  presence  of  the  weak  acids  of  the  tissue  fluids, 
and  indicates  therefore  an  alkaline  color  reaction.  If 
we  remember  that  uncharged  protein  cannot  be  pre- 
cipitated through  the  positively  charged  heavy  metals, 
while  the  proteins  of  the  tissue  fluids  can  at  once  be 
precipitated  by  them,  the  conclusion  is  inevitable  that 
native  protein  carries  a  negative  charge.  This  charge 
can  be  derived  only  from  the  hydroxyl  ions  that  are  split 
off  from  the  salts  of  the  serum,  which,  in  harmony  with 
the  above-described  experiments,  must  be  the  carbonates 
and  phosphates.  If  sodium  bicarbonate  is  added  to  fresh 
non-charged  protein,  this  assumes  a  strong  negative 
charge  even  though  the  resulting  mixture  is  neutral 
toward  litmus  and  acid  toward  phenolphthalein.  In  an 
experiment  conducted  with  such  a  sodium  bicarbonate- 
protein,  it  was  found  that  the  relation  of  nitrogen  at  the 
cathode  was  to  that  at  the  anode  as  3:5;  while  the 
nitrogen  content  of  the  middle  beaker  was  expressed  by  4. 

IV. 

We  are  now  acquainted  with  sufficient  facts  to  study 
more  closely  the  conditions  for  the  precipitation  of 
native  electronegative  protein,  and  to  compare  these 
whenever  necessary  with  those  of  uncharged  or  artificially 
charged  protein. 


ON    THE  ELECTRICAL   CHARGE  OF  PROTEIN.        M7 


Let  us  consider,  first  of  all,  the  precipitation  of  native 
protein  through  neutral  salts  of  the  alkali  metals  and  see 

in  how  far  the  ions  play  an  immediate  role.     The  follow- 
ing table,  in  which  +  indicates  that  the  protein  is  pre 
cipitated,  —  that  it  is  not  precipitated,  gives  a  good  survey 
of  these  relations. 

In  the  vertical  row  of  the  table  arc  arranged  the  positive 
ions  in  the  order  of  their  decreasing  power  to  precipitate 
protein;    in  the  horizontal  row  are  arranged  the   negative- 
ions  in  the  order  in  which  they  inhibit  the  precipitation. 
£P  — >  Increase  i;i  inhibition. 


%  8. 

a 

o 

u 
o 
o 

Q 
I 


S04 

C2H3O2 

CI 

N03 

Br 

I 

CNS 

Li 

+ 

-j_ 

+ 

+ 

Xa 

+ 

+ 

+ 

_i_ 

- 

- 

K 

-j. 

+ 

-|_ 

- 

- 

- 

NH4 

+ 

- 

- 

- 

- 

- 

- 

The  antagonism  between  cation  and  anion  is  indicated 
by  the  appearance  of  one  and  the  same  ion  in  salts  which 
precipitate  and  those  which  do  not  precipitate  protein — 
for  example,  sodium  as  the  sulphate  and  as  the  bromide; 
and  if  we  go  along  still  further  in  the  sodium  scries  the  in- 
hibiting effects  of  iodide  and  sulphocyanate  ions  have  so 
much  the  upper  hand  that  the  presence  of  these  salts  pre- 
vents the  precipitation  of  protein  through  other  salts.  As 
an  actual  matter  of  fact,  the  inhibiting  salts  were  discov- 
ered as  a  consequence  of  the  assumption  of  antagonistic 
ion  effects.  That  it  is  the  positive  metallic  ions  which  are 
the  bearers  of  the  precipitating  power  may  be  concluded 
from  the  fact  that  native  protein  carries  a  negative  charge. 


148  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

Let  us  now  ask  what  will  happen  when  we  try  to  pre- 
cipitate with  neutral  salts  protein  that  has  been  rendered 
electropositive  through  the  addition  of  an  acid.  Theoret- 
ically we  would  expect  that  under  these  circumstances 
the  negative  ions  of  the  salts  would  precipitate  the  pro- 
tein, while  the  metallic  ions  would  have  an  inhibiting  effect. 
And  as  an  actual  matter  of  fact,  we  find  that  when  the 
protein  has  been  acidulated  the  formerly  inhibiting 
bromides,  iodides,  and  sulphocyanates  become  powerful 
precipitants,  and  those  salts  which  formerly  precipitated 
now  inhibit.  In  other  words,  the  signs  cf  the  above  table 
are  reversed;  only  the  precipitating  effect  of  the  negative 
ions  increases  in  the  same  order  as  their  inhibiting  effect 
did  formerly,  while  the  order  of  the  now  inhibiting 
positive  ions  is  just  the  reverse  of  that  given  in  the  table. 

The  following  interesting  fact  has  also  been  found. 
The  same  reversal  in  ionic  effects  as  is  brought  about 
through  acids  can  also  be  brought  about  through  the 
addition  of  the  salts  of  the  alkaline  earths,  Ca,  Ba,  and 
Sr,  to  the  native  protein.  One  may  conclude  from  this 
that  a  change  in  the  sign  of  the  charge  of  the  protein 
solution  from  the  negative  to  the  positive  occurs  in  this 
case  also.  According  to  our  conversion  experiments, 
however,  uncharged  protein  does  not  assume  an  electrical 
charge  through  the  presence  of  the  neutral  salts  of  the 
alkaline  earths,  and  in  consequence  we  have  to  discover 
whether  these  do  not  bring  about  an  acid  reaction  by 
meeting  with  the  salts  contained  in  the  animal  fluids. 
In  order  to  answer  this  question,  let  us  consider  the 
changes  that  are  brought  about  through  the  addition  of 
calcium  chloride  to  a  solution  of  sodium  bicarbonate 
or  disodium  phosphate.     As  is  well  known,  the  two  salts 


ON   THE  ELECTRICAL   CHARGE   OE  PROTEIN.        1 49 

last  mentioned  have  an  alkaline  reaction  in  that  upon 

solution  in  water  they  increase  the  number  of  OH  ions 
present  in  it.  This  is  brought  about  through  the  fad 
that  they  combine  with  water  and  split  hydrolytically  into 
sodium  hydroxide  and  carbonic   and   phosphoric   acids. 

Since,  however,  sodium  hydroxide  is  a  stronger  base  than 
carbonic  and  phosphoric  acids  are  acids,  more  OH  ions 
exist  in  solution  than  II  ions.  If  now  we  imagine  the 
sodium  hydroxide  to  be  replaced  by  the  much  weaker 
calcium  hydroxide,  then  the  concentration  of  the  free 
OH  ions  will  fall  immediately.  The  chemical  reaction 
between  the  alkaline  earths  added  to  an  animal  fluid 
and  the  phosphates  and  carbonates  contained  in  it  must 
also  act  in  this  way — in  other  words,  toward  the  establish- 
ment of  an  acid  reaction  in  the  fluid.  It  can  readily  be 
shown  even  in  an  experiment  with  native  protein  to  which 
an  alkali  has  been  added  and  which  reddens  phenol- 
phthalein  very  strongly  that  an  acid  reaction  is  produced 
in  the  mixture  as  soon  as  calcium  chloride  is  added  to 
it,  as  indicated  by  disappearance  of  the  red  color.  In 
this  way  the  identical  effects  of  acids  and  alkaline  earths 
upon  negatively  charged  protein  have  found  a  ready 
explanation. 

That  the  alkaline  earths  can  act  only  indirectly  through 
their  effects  upon  the  salts  of  the  serum  is  shown  most 
strikingly  by  an  experiment  in  which  calcium  chloride  is 
added  to  salt-free  serum.  If  sodium  iodide  or  sodium 
sulphocyanatc  is  added  to  this  mixture,  no  precipitate  is 
produced.  If,  however,  the  protein  is  rendered  electro- 
positive through  the  addition  of  a  little  acid,  then  the 
sulphocyanatc  at  once  brings  about  a  coarsely  llocculent 
precipitate. 


150  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

We  will  end  with  this  our  discussion  of  observations 
which  indicate  unequivocally  the  great  importance  of 
the  electrical  condition  of  the  proteins  for  their  reactions. 
Since  this  electrical  condition  of  the  proteins  is  deter- 
mined solely  through  the  non-neutral  salts  of  the  tissue 
fluids,  we  can  readily  see  how  important  a  proper  balance 
of  these  salts  must  be  for  the  organism.  One  will  not 
err,  therefore,  in  discovering,  in  the  purposeful  arrange- 
ments existing  in  the  animal  body  against  the  presence  of 
too  large  amounts  of  acid,  instruments  of  protection  for 
the  proper  physiological  electrical  charge  of  the  proteins. 

V. 

We  are,  no  doubt,  justified  in  presupposing  that  con- 
ditions within  the  cell  are  very  analogous  to  those  found 
in  the  tissue  fluids.  Hober,  for  example,  has  found  in 
an  excellently  arranged  experiment  that  the  red  blood- 
corpuscles  move  to  the  anode — in  other  words,  are  nega- 
tively charged  under  normal  circumstances  and  retain 
this  charge  under  a  great  variety  of  conditions.  If  they 
possess  in  this  wise  an  electrical  charge  which  is  similar 
to  that  of  the  blood  serum,  they  can  nevertheless  show 
variations  in  their  behavior,  as,  for  example,  under  the 
influence  of  acids.  In  an  isotonic  cane  sugar-sodium 
chloride  mixture  they  become  electropositive  under  the 
influence  of  carbonic  acid,  a  change  that  is  again  reversed 
when  the  carbonic  acid  is  removed.  It  seems,  therefore, 
as  though  the  red  blood-corpuscles  suffer  a  complete 
change  in  electrical  reaction  when  they  pass  through 
the  pulmonary  circuit. 

The  essence  of  the  electrical  condition  of  cells  can  be 


ON    THE  ELECTRICAL    CHARGE   OF  PROTEIN.        151 

demonstrated  without  difficulty  on  the  electri<  al  properties 
of  the  proteins.  Every  attempt  to  explain  the  phenomena 
observed  ends  with  the  question,  J  low  dues  a  protein 
partiele  floating  about,  for  example,  in  a  dilute  hydro 
chloric  acid  assume  an  electropositive  charge  when  the 
acid  contains,  as  we  know,  an  equal  number  of  positive 
H  ions  and  negative  CI  ions  ?  It  is  evident  that  this  is  only 
possible  when  protein  takes  up  more  positive  H  ions  than 
negative  CI  ions,  or,  as  it  is  ordinarily  stated,  when  the 
protein  is  semi-permeable  to  ions.  The  same  holds  in 
the  case  of  alkalies  for  the  OH  ions.  Many  cells  seem 
to  have  this  same  power,  and  Hober  has  rendered  it 
probable  that  red  blood-corpuscles  become  positive  when 
treated  with  carbonic  acid,  because  they  become  per- 
meable for  some  of  the  negative  ions  which  they  contain 
and  which  leave  the  red  blood-corpuscles,  thereby  allowing 
an  excess  of  positive  ions  to  remain  behind. 

Ostwald  was  no  doubt  the  first  to  try  to  discover 
in  the  semi-permeability  for  ions  the  cause  of  the  electrical 
phenomena  observed  in  animal  cells,  and  this  suspicion 
has  recently  attained  a  very  considerable  degree  of  proba- 
bility. Oker-Blom  and  later  Bernstein  have  further 
developed  this  idea  for  the  electrical  phenomena  observed 
in  muscle  and  nerve,  and  sought  experimental  evidence 
for  its  support.  If  we  imagine  the  surface  of  the  muscle 
fibril  to  be  more  permeable  for  the  positive  ions  than  for 
the  negative  ions  contained  in  the  muscle,  then  the  muscle 
must  carry  a  positive  charge  externally  and  a  negative 
one  within.  When  two  electrodes  are  laid  upon  the 
surface  of  an  uninjured  muscle,  points  having  a  different 
electrical  potential  are  not  touched,  and  the  muscle 
shows  no  current. 


IS2  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

As  soon,  however,  as  the  one  electrode  is  placed  upon 
an  artificially  produced  cross-section  of  a  muscle — in  other 
words,  along  the  contents  of  the  fibrils — the  well-known 
current  of  rest  passes  in  the  outer  circuit  toward  the 
negative  exposed  portions  of  the  muscle  plasma.  The 
experiments  of  Bernstein  have  shown  that  this  current 
follows  very  accurately  the  typical  laws  governing  ionic 
concentration  chains.  The  same  holds  for  the  current 
of  rest  in  nerves.  Stimulation  of  the  nerve  brings  about 
the  well-known  phenomenon  of  negative  variation,  in 
that  it  alters  the  permeability  for  ions. 

Similar  phenomena  are  observed  in  the  electric  organ 
of  the  torpedo,  which  has  been  studied  by  Bernstein 
and  Tschermak.  This  organ  consists  of  numerous 
plate-like  cells  arranged  upon  each  other  in  a  way  similar 
to  the  plates  of  a  voltaic  pile  and  possessing  a  nervous 
end  brush  upon  one  side  only. 

When  through  nervous  stimulation  this  side  becomes 
more  permeable  for  negative  ions,  an  electric  shock  is 
produced  through  summation  of  the  charges  of  the  single 
cells,  the  intensity  of  which  does  not  need  to  exceed  that 
of  a  muscle  current.  As  measurements  indicate,  the  pro- 
duction of  electricity  in  the  electric  organ  seems  also  to 
follow  in  the  main  the  thermodynamic  laws  governing 
concentration  chains. 

Let  us  return  once  more  to  the  current  of  rest  in  muscle, 
which  we  have  attributed  to  the  semi-permeability  of  the 
plasma  membranes  for  ions.  If  we  imagine  the  per- 
meability of  this  plasma  membrane  to  be  altered  through 
some  agency  that  precipitates  protein  or  causes  it  to  go 
into  solution,  then  we  may  expect  parallel  variations  in 
the  current  of  rest.     When  Hober  dipped  the  surface  of 


ON   THE  ELECTRICAL   CHARGE   OF  PROTEIN.        153 

freshly  cut  frog's  muscles  into  sail  solutions  of  various 
kinds  and  measured  the  current  of  rest,  he  found  that 
the  effects  of  the  different  salts  in  this  regard  arrange 
themselves  Into  a  table  similar  to  that  given  above  for 
the  precipitation  of  electropositive  protein.  The  sign 
indicating  a  precipitation  corresponds  with  a  reversal 
in  the  current  of  rest,  while  that  indicating  a  solution 
with  the  normal  current  of  rest. 

The  electrical  behavior  of  proteins  is  of  importance  to 
the  histologist  also  for  a  proper  understanding  of  the 
important  cellular  reactions  which  take  place  in  fixation 
and  staining.  In  spite  of  the  fact  that  all  the  different 
portions  of  the  cell  are  exposed  to  the  same  action  of 
the  fixing-agent,  be  this  an  indifferent  substance,  such  as 
alcohol,  or  one  imposing  a  positive  charge,  such  as  a 
solution  of  an  acid  or  a  heavy  metal,  the  separate  con- 
stituents of  the  cell  react  differently  toward  acid  and 
basic  dyes.  Through  the  investigations  of  Biltz  in  par- 
ticular, the  identity  of  the  process  of  dyeing  and  colloidal 
reactions  seems  to  be  well  established,  so  that  we  may 
assume  that  different  portions  of  a  cell  may  show  different 
electrical  states  when  exposed  to  the  same  external  con- 
ditions. We  will  carry  this  discussion  no  further,  but 
will  only  draw  attention  to  an  observation  which  is 
intimately  connected  with  our  own.  E.  Mayr  (Graz) 
has  studied  under  Bethe's  direction  the  influence  of 
salts  upon  the  fixation  and  precipitation  of  nervous  tissue- 
These  studies  have  shown  that  the  effects  of  ions  upon  the 
preservation  and  staining  qualities  of  nerve  fibres  arrange 
themselves  in  a  way  similar  to  the  table  given  on  page  147 
for  the  precipitation  of  electronegative  protein,  while  the 
order  of  the  ions  is  just  the  reverse  and  corresponds,  in 


154  PHYSICAL  CHEMISTRY  IN  MEDICINE. 

the  main,  with  that  for  the  precipitation  of  electropositive 
protein  when  the  ions  are  arranged  in  the  order  in  which 
they  render  visible  certain  elements  of  the  ganglion  cells, 
such  as  Nissl  bodies  and  nucleoli. 

But  that  an  electrical  difference  exists  between  nuclear 
substance  and  cell  protoplasm  even  in  the  living  cell  is 
rendered  probable  through  many  facts.  Ralph  Lillie 
found  a  difference  in  the  direction  in  which  spermatozoa 
and  cells  rich  in  protoplasm  move  in  the  electric  current, 
and  Martin  H.  Fischer  and  Wolfgang  Ostwald 
have  already  tried  to  give  a  physico-chemical  theory  of 
fertilization.  However  imperfect  these  attempts  must 
of  necessity  seem,  the  successful  establishment  of  a  certain 
parallelism  between  those  factors  which,  on  the  one  hand, 
bring  about  artificial  parthenogenesis  and,  on  the  other, 
cause  a  precipitation  of  solid  colloids  is  of  permanent 
value.  The  similarity  of  the  formation  of  the  astrosphere 
about  the  spermatozoon  which  has  entered  an  egg  with 
certain  precipitations  produced  in  colloids  has  been  re- 
peatedly noticed  by  investigators. 

But  we  will  keep  from  entering  fields  which  have 
as  yet  been  but  little  opened  experimentally,  and  in  closing 
point  out  a  relation  which  by  itself  is  not  without  general 
interest  and  which  may  also  be  of  service  to  the  investigator. 

Between  the  reactions  of  colloids  which  take  place 
with  an  equalization  of  electrical  differences  and  the 
reactions  of  the  immune  bodies  there  exists  a  relation 
which  is  as  intimate  as  anything  can  be,  an  idea  which 
has  already  been  illustrated  in  another  place.  More- 
over, a  more  than  accidental  similarity  seems  to  exist 
between  immune  reactions  and  the*  changes  which  take 
place  in  the  process  of  fertilization. 


ON   THE   ELECTRICAL   CHARGE  OF  PROTEIN.        155 

Wc  know  that  the  spermatozoon  reacts  specifically  with 
the  egg,  that  this  specificity  is,  however,  not  absolute, 
as  shown  by  the  production  of  bastards.  This  specificity 
can  also  be  altered  through  different  chemicals,  as  shown 
by  the  remarkable  hybridization  experiments  of  Loeb. 
We  see  further  that  the  spermatozoon  becomes  immo- 
bilized within  the  egg,  in  that  a  kind  of  precipitation,  the 
formation  of  the  astrosphere,  a  characteristic  morpho- 
logical sign  of  fertilization,  starts  from  the  spermatozoon. 

Let  us  compare  with  this  picture  such  a  process  as  the 
agglutination  of  bacteria  through  immune  serum.  Here 
also  there  exists  a  specificity  which  is,  however,  by  no 
means  absolute,  and  here  also  an  immobilization  in  the 
scrum  of  the  mobile  bacterium.  According  to  the 
pleasing  idea  of  Paltauf,  we  are  dealing  in  this  case 
with  the  formation  of  a  precipitate  about  the  capsule  of 
the  bacterium,  something  similar,  therefore,  to  the  change 
which  occurs  about  the  spermatozoon  which  has  pene- 
trated an  egg.  The  specific  effects  of  the  immune  bodies 
can  also  be  altered  through  chemicals. 

They  are  always  associated  problems,  therefore,  which 
arise  in  this  or  the  other  illustration  used,  and  they  all 
spring  from  the  manifold  similarity  which  exists  between 
the  colloids  of  the  organism  within  and  without  the  cells 
and  which  is  determined  to  so  great  a  degree  by  the 
electrical  properties  of  the  colloids. 

There  can  be  little  doubt  that  out  of  the  study  of  the 
physico-chemical  properties  of  the  colloids  there  will 
spring  a  new  bud  of  physical  physiology  in  which  the 
application  of  the  modern  teachings  of  electricity  will 
play  a  primary  role.     The  physiology  which  recognizes 


156  PHYSICAL   CHEMISTRY  IN  MEDICINE. 

in  the  neighboring  sciences  of  physics  and  chemistry  that 
profound  revolutionizing  influence  of  the  newer  electrical 
investigations,  which  do  not  stop  before  even  the  most 
sacred  and  fundamental  conceptions  of  this  subject,  must 
consider  it  as  a  next  most  worthy  task  to  guarantee  itself 
its  share  in  the  new  conquests  of  scientific  knowledge. 


N  t~^ 


